Epidemiology of nematode parasites of sheep around Jimma,southwestern Ethiopia

An investigation was made into the epidemiology of nematode infections of sheep in two districts of Jimma zone, southwestern Ethiopia. We used two approaches—long-term monitoring of identified sheep for nematode infection and abattoir or market survey for analysis. In the first monitoring regime, we used 80 lambs [40 sheep (20 per sex) from each district (Dedo and Yebu)] averaging 4–5 months of age. Faecal egg counts (FEC), packed cell volume (PCV) and body weight changes were monitored over a period of 1 year. Additionally, faecal samples were collected (on a weekly basis) from sheep brought to abattoir/market for 1 year to monitor faecal egg counts. The nematode parasite burden, as judged by FEC and PCV, was generally low indicating that the climatic conditions are not conducive to the development and survival of nematode eggs and the free-living stages; hence, little transmission occurred. In the experimental flocks, the highest FEC and lower PCV were recorded during the long rainy season (June to September) with peak in August and September. Faecal samples collected from abattoir/market also followed the same trend. Results from experimental sheep indicated that location had a significant (P < 0.01) effect on FEC, PCV and average daily body weight gain. The FEC and PCV for sheep in Yebu (mid-altitude) district were 126 ± 3.33 and 30.6 ± 0.26, whereas the values for Dedo (highland) were 93 ± 4.35 and 32.0 ± 0.21, respectively. The results indicate that the highland areas are comparatively less favourable to the survival and development of nematodes. Female lambs had lower FEC and higher PCV compared to male lambs (P < 0.05). The overall nematode parasite challenge in the area, however, is low. We, therefore, recommend rotational grazing management combined with monitoring parasite load and selective treatment to reduce productivity loses and pasture contamination.     

Epidemiological observations and heterosis analysis of gastrointestinal nematode parasitism in Suffolk, Gulf Coast Native, and crossbred lambs.

A crossbreeding program was conducted to evaluate the resistant status to gastrointestinal nematode parasite infection in crossbred (F1) lambs and their Suffolk and Gulf Coast Native (Native) breed counterparts. A total of 253 lambs were included in the study over 2 years. Fecal egg count (FEC) and blood packed cell volume (PCV) of 18-20 monitor lambs of each breed group in each year were collected every other week from birth to 24-30 weeks of age. The FEC and PCV of all lambs were determined at weaning (11-12 weeks of age) and at three subsequent times when anthelmintic treatment was administered. Nematode counts of wether lambs were obtained at 30 weeks of age in the first year. The epidemiological patterns of FEC and PCV of each breed group were similar in both years. The Suffolk group consistently showed the highest FEC and the lowest PCV. Conversely, the Native group had the lowest FEC and highest PCV. For the most part, all parameters for the F1 group fell intermediate to the Native and Suffolk groups. Nematode count followed the same pattern. Heterosis analysis showed that FEC, PCV, nematode count and weight gain of the F1 group favored the Native group. These results suggested that crossbreeding Suffolk to Native sheep may be a suitable way to produce lambs with improved resistance to gastrointestinal nematode infection, but production may be compromised.     

Performance of hair sheep composite breeds: resistance of lambs to Haemonchus contortus

This study was designed to evaluate breed differences in resistance to Haemonchus contortus in lambs. A total of 181 ewe lambs representing crossbred Dorsets (DO) and Dorpers (DP; out of 1/2-Dorset, 1/4-Rambouillet, 1/4-Finnsheep ewes) and straight-bred Katahdins (KT) were evaluated over 3 yr. An additional 144 DO, DP, KT, and Barbados Blackbelly x St. Croix (HH) wethers were evaluated over 2 yr. Lambs were weaned at 60 to 90 d of age. After deworming at about 4 mo of age, ewe lambs received approximately 10,000 infective larvae and were evaluated for parasite resistance in drylot, whereas wethers were evaluated on pasture under conditions of natural infection. Each sex was analyzed separately. Egg counts per gram of feces (FEC), log-transformed FEC (LFEC), packed cell volumes (%), and body weights (kg) measured at 3, 4, 5, and 6 wk after deworming and reinfection were analyzed. Breed influenced all traits (P < 0.05) except BW in ewe lambs and PCV in wethers. Year and week influenced (P < 0.05) all traits. At most times, DP had the highest FEC, DO had the lowest PCV, and KT and HH had lower FEC and higher PCV than either DO or DP. Clearly, Dorper sheep were not more resistant to parasites than DO, but they were able to cope with infection better by maintaining similar or higher (P < 0.05) PCV and similar BW. Katahdin and HH were more resistant, with lower FEC (P < 0.05) than DO or DP. Breed differences were more apparent when infection levels were higher; DO and DP were less affected when infection levels were low and when animals were on a better plane of nutrition. Caribbean hair sheep originated in hot, humid regions of West Africa. They and the derivative Katahdin breed seem relatively resistant to parasitism. The Dorper, in contrast, was developed in more arid regions and exhibited little parasite resistance.     

Performance and nematode infection of ewe lambs on intensive rotational grazing with two different cultivars of <Emphasis Type="Italic">Panicum maximum</Emphasis>

The daily live weight gain (DLWG), faecal nematode egg counts (FEC), and packed cell volume (PCV) of Suffolk, Ile de France and Santa Inês ewe lambs were evaluated fortnightly for 56 days in the dry season (winter) and 64 days in the rainy season (summer) of 2001-2002. The animals were distributed in two similar groups, one located on Aruana and the other on Tanzania grass (Panicum maximum), in rotational grazing system at the Instituto de Zootecnia, in Nova Odessa city (SP), Brazil. In the dry season, 24 one-year-old ewe lambs were used, eight of each breed, and there was no difference (p > 0.05) between grasses for DLWG (100 g/day), although the Suffolk had higher values (p < 0.05) than the other breeds. In the rainy season, with 33 six-month-old ewe lambs, nine Suffolk, eight Ile de France and 16 Santa Inês, the DLWG was not affected by breed, but it was twice as great (71 g/day, p < 0.05) on Aruana as on Tanzania grass (30 g/day). The Santa Inês ewe lambs had the lowest FEC (p < 0.05) and the highest PCV (p < 0.05), confirming their higher resistance to Haemonchus contortus, the prevalent nematode in the rainy season. It was concluded that the best performance of ewe lambs on Aruana pastures in the rainy season is probably explained by their lower nematode infection owing to the better protein content of this grass (mean contents 11.2% crude protein in Aruana grass and 8.7% in Tanzania grass, p < 0.05) which may have improved the immunological system with the consequence that the highest PCV (p < 0.05) observed in those animals.     

Effect of dexamethasone treatment on the immune response of Gulf Coast Native lambs to Haemonchus contortus infection

Neonatal and weaner Gulf Coast Native (Native) lambs were studied to determine whether an immunological basis underlies their natural resistance to Haemonchus contortus infection. Neonatal Native lambs (n = 8) and weaner Native lambs (n = 15) were randomly assigned to a treatment or a control group. Lambs in the treatment group received dexamethasone by intramuscular injection three times a week for 10 weeks (neonatal) and 15 weeks (weaners). All lambs were monitored for fecal egg count (FEC), blood packed cell volume (PCV), and white blood cell differential counts on a weekly basis for the duration of the studies. Neonatal lambs were kept on pasture with their dams and weaner lambs were dewormed at weaning and kept in pens where they received trickle infections. Serum antibody titers to H. contortus whole worm antigen (WWA) were determined using ELISA. Lymphocyte proliferation assays on peripheral blood mononuclear cells (PBMC) were done to assess lymphocyte function. All lambs were vaccinated with killed Brucella abortus strain 19 to assess the effect of dexamethasone treatment on antibody response. All lambs were necropsied at the end of each study to recover the contents of the gastrointestinal tract for nematode enumeration and identification. The results showed that mean FEC and mean PCV of the treatment group was significantly higher and lower, respectively, than in the control group in both neonatal and weaner lambs from weeks 6 and 5, respectively. At necropsy, total nematode count was significantly higher in treatment groups than in the control groups. Serum antibody titers to H. contortus WWA were significantly lower in treated groups than in control groups. Treatment groups showed a consistent depression in lymphocyte percentage being significantly lower from week 6 in both neonatal and weaner lambs. No differences were found in the response of PBMC to mitogen stimulation between the groups. Lambs in the control groups showed strong positive brucellosis card tests and the treatment groups did not. Dexamethasone treatment resulted in depression of the immune response and loss of natural resistance of Native lambs to H. contortus infection. The results of these studies suggest that some aspects of the immune response may underlie the natural resistance of Native sheep to H. contortus infection.     

Field study on nematode resistance in Nelore-breed cattle

The present study evaluated Nelore cattle with different degrees of resistance to natural infections by gastrointestinal nematodes. One hundred weaned male cattle, 11-12 months of age, were kept on the same pasture and evaluated from October 2003 to February 2004. Faecal and blood samples were collected for parasitological, haematological and immunological tests. In February 2004, the 10 most resistant and the 10 most susceptible animals were selected based on individual means of nematode faecal egg counts (FEC). Such animals were slaughtered for worm burden determination and nematode species identification. The repeatability estimates for FEC (+/-S.D.), log-transformed FEC and packed-cell volume (PCV) in all animals were 0.3 (+/-0.05), 0.26 (+/-0.04) and 0.42 (+/-0.05), respectively. The resistant group showed lower FEC and worm burdens than the susceptible group (P<0.05). There were no significant differences between groups regarding mean body weight, weight gain, PCV and total serum protein values (P>0.05). The resistant group showed higher total serum IgE levels (P<0.05) and higher mean eosinophil blood counts. However, the latter was statistically significant only 42 days after the beginning of the study. Nematodes Cooperia punctata and Haemonchus placei were predominant and the correlation between Cooperia and Haemonchus burdens was 0.64 (P<0.05), which indicated that animals presenting increased numbers of one of those genera probably had increased numbers of the other. The current study provides further evidence of IgE active role in nematode immunity and suggests that total serum IgE level might serve as an additional marker to select Nelore cattle that are responsive to H. placei and C. punctata infections.     

Impact on productivity of peri-parturient rise in fecal egg counts in Creole goats in the humid tropics

The control of gastrointestinal nematodes requires an understanding of their epidemiology so that particular parasite stages can be targeted. Dam infection during early lactation is one example of this in ruminant nematode infections. The existence of the peri-parturient relaxation in immunity and its impact on productivity were examined in a Creole goat flock from Guadeloupe, exposed to mixed natural infection (predominantly Haemonchus contortus and Trichostrongylus colubriformis). A total of 1,511 l were obtained from 909 does resulting from 463 dams and 150 sires. Fecal and blood samples were collected at kidding before anthelmintic drenching, 4 and 6 weeks after kidding. The traits analyzed were logarithm transformed fecal egg counts (FEC), packed cell volume (PCV), and logarithm transformed blood eosinophilia counts (EOS) for does at each sampling point and changes in these during the postpartum period. With the exception of the PCV values measured at kidding, lactating does had significantly higher FEC and lower PCV than control dry does at every sampling point. Geometric means of FEC in lactating does were 819 +/- 174, 677 +/- 146 and, 699 +/- 160 eggs per gram (EPG) at kidding, 4 and 6 weeks after kidding respectively. Geometric means of FEC in dry does were 187 +/- 57, 89 +/- 28, 133 +/- 43 at these time points, respectively. EOS differences were not consistent between groups and probably not specific enough for variations in Creole goats' peri-parturient rise to be discussed. As does aged, their egg output decreased and primiparous does always had greater egg output than multiparous ones. Overall, does' FEC at 4 weeks after kidding decreased by 1.3% each year. The higher the litter size, the higher the FEC at kidding and inverse applied for PCV measurements. Does that stopped lactating had significantly lower FEC and higher PCV values than lactating does with low milk yields. Higher infection rates during early lactation in Creole goats were recorded in does with lower maternal ability assessed by the average daily weight gain of kids between 10 and 30 days of age. Kids from dams with higher FEC (i.e. >600 EPG higher than corresponding does) had 17% lower average daily weight gain between 30 and 70 days postpartum and were approximately 1 kg lighter at weaning than kids from dams with lower FEC. Thus, it is clear that a peri-parturient rise in FEC exists in Creole goats. By controlling the intensity of this peri-parturient rise in FEC, herd health and productivity could be substantially improved.     

Comparison of naturally acquired parasite burdens among Florida native, Rambouillet and crossbreed ewes.

The response to natural infection by gastrointestinal nematodes was evaluated in three groups of lambing mature ewes: 16 Florida Native; 21 Rambouillet; and 18 1/2 Florida Native x1/2 Rambouillet (F1 generation). Fecal egg counts (FEC), packed cell volume (PCV) and plasma protein levels were determined periodically through a one-year period. The highest FEC was recorded in Rambouillet ewes, with most of the means higher than 1000 eggs per gram (EPG). Florida Native and F1 ewes showed similar trends in FEC, with most of the means below 500 EPG. The highest mean PCV values were recorded in Florida Native ewes, followed in decreasing order by F1 and Rambouillet ewes. F1 ewes showed the lowest plasma protein levels and Florida Natives the highest. Fecal cultures revealed the highest percentages of Haemonchus larvae in Rambouillet ewes (>64%) and the lowest percentages in Florida Native ewes. Florida Native and F1 ewes were more resistant to gastrointestinal nematode infections than were Rambouillet ewes. High negative correlation coefficients between FEC x PCV and FEC x plasma protein levels coincided with peaks in mean FEC of Rambouillet (May and July), Florida Native and F1 ewes (October). This study showed that crossbreeding Rambouillet and Florida Native sheep resulted in the production of F1 ewes resistant against gastrointestinal nematode infections.     

Control of gastrointestinal nematodes with copper oxide wire particles in a flock of lactating Polypay ewes and offspring in Iowa, USA

Copper oxide wire particles (COWP) have been used to reduce infection of Haemonchus contortus in hair breed lambs in southeastern USA without signs of copper toxicity. However, copper sensitivity among breeds and regions varies. The objective was to determine the effectiveness and safety of COWP in lactating Polypay ewes and their offspring grazing alfalfa/bluegrass pasture in a rotational grazing system. Mature Polypay ewes were administered 0, 0.5, 1, or 2 g (n=8 or 9/dose) COWP approximately 60 days after lambing in mid-July 2005. Their offspring were administered 0 (n=6), 0.5 or 0.75 g (n=9), 1 or 2 g (n=6) COWP 2 weeks later in late July. The primary gastrointestinal nematode was H. contortus (70%). Between Days 7 and 35, FEC were greater in 0 and 0.5 g COWP groups compared with ewes administered 2 g COWP (COWP x day, P<0.004). PCV decreased in all groups of ewes between Days 0 and 21 (day, P<0.001). Aspartate aminotransferase (AST) activity, a measure of liver copper levels, and body weight was similar among groups of ewes. FEC decreased within 7 days in COWP-treated compared with untreated lambs and remained low throughout experiment (COWP x day, P<0.05). PCV increased in COWP-treated lambs between Days 7 and 35 and decreased in untreated lambs between Days 0 and 21 (COWP x day, P<0.009). AST activity was similar among groups of lambs. Administration of 2 g COWP to ewes prevented a rise in FEC, but a dose of 0.5 g was ineffective as an anthelmintic. Administration of all doses of COWP to lambs decreased FEC and increased PCV compared to untreated lambs. There were no signs of copper toxicity in ewes or lambs. Alternative suppression of H. contortus infections may be necessary in ewes, but COWP was effective in H. contortus management for lambs.     

The modulatory influence of Trypanosoma brucei on challenge infection with Haemonchus contortus in Nigerian West African Dwarf goats segregated into weak and strong responders to the nematode

Although Nigerian West African Dwarf (WAD) goats are relatively resistant to infection with Haemonchus contortus and are also trypanotolerant, natural outbreaks of both infections are known to occur. Despite their relative resistance to H. contortus WAD goats nevertheless show variability in response phenotype and it was of interest to examine the effect of this variability on the outcome of concurrent trypanosome infection. Trypanosoma brucei infections were established in goats that were initially classified as good or poor responders to H. contortus. Thirty-nine goats were exposed to an escalating infection with H. contortus, and on the basis of their mean faecal egg counts (FEC) were allocated to high FEC (poor responders, 18 goats with the highest FEC) or low FEC (good responders, 18 goats with the lowest FEC) classes. Nine uninfected naive control goats were included to provide reference baseline values. Retrospective analysis of parasitological and pathological parameters after allocation into high/low FEC classes showed that FECs differed significantly, in both classes packed cell volume (PCV) values fell relative to naive controls, neither class lost weight and both generated marked IgG responses. All goats received anthelmintic on day 61, half of each group was infected with 50 million trypanosomes and on day 67, excepting the controls, all goats were challenged with 3000 L3 of H. contortus. Trypanosome parasitaemia was generally low, and marginally, but not significantly, higher in the low compared with high FEC class, peaking 12-16 days after exposure in both groups and then falling to below microscopically detectable levels (although still detectable by sub-inoculation into mice) by week 3. At autopsy (days 109/110), worm burdens were significantly higher in the trypanosome-infected goats from the high FEC class, relative to all other groups. Trypanosome infected goats showed a tendency (although not significant) towards higher FEC and, irrespective of their FEC class, had lower PCV values although body weight did not vary significantly. All goats challenged with H. contortus had higher antibody levels than naive controls, but neither trypanosome infection nor FEC class affected the magnitude of responses. These results confirm that WAD goats comprise a range of response phenotypes to initial H. contortus infection and that trypanotolerance is a key trait of this breed. Although immunity to nematode infection develops even in poor responders, these animals harbour higher nematode burdens during concurrent infection with T. brucei.     

Evaluation of the phenotypic performance of a Red Maasai and Dorper double backcross resource population: indoor trickle challenge with Haemonchus contortus

Six F(1) Dorper (D) x Red Maasai (R) rams were mated to both D and R ewes to produce backcross lambs. These six double backcross resource families are being analysed to identify quantitative trait loci that may be controlling resistance to gastro-intestinal (GI) nematode parasites, mainly Haemonchus contortus. After assessing the phenotypic performance of the lambs following exposure to natural infections, the surviving lambs were drenched and moved indoors for an artificial challenge with H. contortus along with straightbred D and R lambs. A total of 1317 lambs were included in the analyses consisting of 523 3/4D, 580 3/4R, 87 D and 127 R. The D lambs were significantly and consistently heavier than R lambs and 3/4D were significantly heavier than the 3/4R lambs. The difference between the backcrosses was about half of that between the straightbreds. Resistance was assessed in terms of faecal egg counts (FEC) and total worm counts (TWC) at necropsy while packed cell volume (PCV) was used to assess resilience to weekly oral doses of 2500 infective larvae of H. contortus. No significant breed differences were observed for log transformed FEC (LFEC). A significant breed difference in PCV was recorded. The backcrosses had the higher values and while no differences were observed between the straightbreds, 3/4D had significantly higher PCV than the 3/4R. Despite the absence of breed differences in FEC the R and the 3/4R had significantly fewer worms than the D and the 3/4D. The D had significantly longer worms than the R and the 3/4D had significantly longer worms than the 3/4R. Worms recovered from D had more eggs than those recovered from R. Similarly worms from 3/4D contained more eggs than those from 3/4R. Thus, on a breed basis the breed with more worms had longer worms. In contrast, when, in a small part of the experiment two doses of larvae were used to check for any breed by dose interactions, worms from the low dose (and hence fewer worms) animals were longer. We postulate that in fast growing hosts like the D, worms also have a better potential for growth and reproduction than in hosts that have less potential for growth. The overall correlation coefficient between PCV and LFEC was -0.67 while that between LFEC and LTWC was 0.72. From these results it is clear that the R do not respond to the artificial challenge the way they do to natural infection suggesting that phenotyping of R and R cross lambs for purposes of selecting those that are resistant or susceptible is best done under natural challenge.     

Inheritance of fecal egg count and packed cell volume and their relationship with production traits in sheep infected with Haemonchus contortus

This study describes responses to artificial infection with Haemonchus contortus in ewes and lambs of 50% Dorset, 25% Rambouillet, and 25% Finn-sheep ancestry and provides estimates of genetic parameters for measures of parasite resistance. One hundred ninety-eight ewes out of 64 sires, and 386 lambs out of 25 sires were evaluated in autumn and spring of 2 yr. Ewes were dewormed shortly after weaning their lambs and lambs were dewormed at about 120 d of age. One week after deworming, ewes and lambs were dosed with approximately 10,000 infective larvae of H. contortus. After infection, BW, fecal egg counts (FEC), and packed cell volume (PCV) were measured weekly for 7 wk in lambs kept in drylot and fortnightly for 11 wk in ewes on pasture. Summary traits were defined as initial PCV, mean BW across all times, and means for PCV (MPCV) and log-transformed FEC (MLFEC) at wk 3 to 7 after infection for lambs and wk 3 to 11 after infection for ewes. Ewes and lambs did not lose weight overall in any year or season, but there was no consistent effect of year or lambing season on mean LFEC or mean PCV during infection in either ewes or lambs. Yearling ewes were less resistant to infection than older ewes, with lower PCV (P < 0.05) and higher LFEC (P < 0.05). During infection, PCV was positively correlated with BW and negatively correlated with LFEC in both ewes and lambs. In lambs, heritabilities were 0.39 (P < 0.01) for PCV, 0.10 (P < 0.05) for LFEC across all measurement times, and 0.19 (P < 0.01) for three measures of LFEC taken at the peak of infection. Heritability estimates for ewes were 0.15 (P < 0.05) for PCV and 0.31 (P < 0.01) for LFEC. Repeatabilities for LFEC and PCV across measurement times were moderate in ewes and lambs. Correlations between dam and lamb records for MLFEC were generally low, suggesting different mechanisms of resistance in lambs and nonlactating ewes. Ewes with higher genetic merit for growth as lambs were less resistant to infection as adults, but genetic merit for fertility and prolificacy were not related to parasite resistance. Lambs with higher genetic merit for body weight were more resistant to infection. Selection for resistance to H. contortus is therefore possible and should not adversely affect growth of lambs and fertility of ewes in this production environment.     

Gastrointestinal nematode infections in small ruminants under the traditional husbandry system during the dry season in southern Ethiopia

A cross-sectional study was conducted from November 2008 to February 2009 to investigate the prevalence and intensity of infection and risk factors of gastrointestinal (GI) nematodes in small ruminants kept under the traditional husbandry system in two districts in southern Ethiopia. Faecal samples collected from a total of 510 small ruminants (284 sheep and 226 goats) and analysed by a modified McMaster technique revealed that 222 animals (43.5%) were found to be infected with one or more GI nematodes. Five identical genera of nematodes were found in both sheep and goats, which in order of predominance were Haemonchus (56.3%), Trichostrongylus (39.6%), Oesophagostomum (22.9%), Trichuris (21.6%) and Bunostomum (10.4%). No significant (p > 0.05) differences were observed between sheep and goats proportions except for Trichuris (p < 0.05). In both sheep and goats, most of the animals were heavily infected showing faecal egg counts (FECs) above 1,200 epg. Sheep had a significantly (p < 0.05) higher mean FEC than goats. In sheep and goats, both the prevalence of GI nematodes and mean FEC were significantly (p < 0.001) associated with body condition score and faecal consistency but not with district, sex and age (p > 0.05 for each factor). In conclusion, the observation of a strong association of GI nematodes with poor body condition coupled with heavy intensity of infection in the majority of infected animals and an abundance of nematode genera of widespread economic and pathological significance warrants the institution of appropriate control measures that should necessarily include improvement of the nutritional status of the animals.     

Resistance of Santa Ines, Suffolk and Ile de France sheep to naturally acquired gastrointestinal nematode infections

A study was conducted to assess the breed resistance against nematode infections in Santa Ines, Ile de France and Suffolk male lambs over a 9-month period in S?o Paulo state, Brazil. Lambs were born during the winter (year 2000) and were weaned at 2 months of age. The animals were then housed and treated with anthelmintics to eliminate natural infections by gastrointestinal nematodes. In late October 2000, lambs were placed in a paddock, where they stayed until August of the following year. Fecal and blood samples were taken from each animal every 2 weeks. On the same day, a pasture sample was collected to determine the number of infective larvae on the herbage. To prevent deaths, individual treatment with anthelmintics was provided to lambs with fecal egg counts (FEC) higher than 4000 eggs per gram (EPG) or with a packed cell volume (PCV) lower than 21%. In August 2001, all animals were slaughtered and the worms present in samples of the gastrointestinal contents were identified and counted. Most of the Suffolk and Ile de France sheep received three to six anthelmintic treatments over a period of 7 months, while most of the Santa Ines were not treated. Reductions in PCV and plasma protein values associated with high FEC and worm burdens were recorded, particularly, in Suffolk and Ile de France lambs. Haemonchus contortus and Oesophagostomum columbianum burdens and number of nodular lesions caused in the large intestine by O. columbianum larvae were significantly lower in Santa Ines sheep. All three breeds showed similar Trichostrongylus colubriformis worm burdens. The relative resistance of Santa Ines young male sheep was superior to that of Suffolk and Ile de France sheep.     

Interaction between copper oxide wire particles and Duddingtonia flagrans in lambs

An experiment was completed to determine if copper oxide wire particles (COWP) had any effect on the activity of the nematode-trapping fungus Duddingtonia flagrans in growing lambs. COWP has been used recently as a dewormer in small ruminants because of nematode resistance to anthelmintics. D. flagrans has been used to control free-living stages of parasitic nematodes in livestock. Katahdin and Dorper lambs, 4 months of age, were administered no or 4 g COWP (n=24/dose) in early October 2003. Haemonchus contortus was the predominant gastrointestinal parasite during the trial, which was acquired naturally from pasture. Half the lambs from each COWP group were supplemented with corn/soybean meal with or without D. flagrans for 35 days. Fecal egg counts (FEC) and packed cell volume (PCV) were determined weekly between days 0 (day of COWP administration) and 35. Feces from lambs in each treatment group were pooled and three replicates per group were cultured for 14 days at room temperature. Larvae (L3) were identified and counted per gram of feces cultured. Treatment with COWP was effective in decreasing FEC, which remained low compared with FEC from lambs not treated with COWP. This led to an increase in PCV in these lambs (COWP x day, P<0.001). Number of larvae was decreased in feces from lambs treated with COWP and D. flagrans between days 14 and 35 compared to the other groups of lambs (COWP x D. flagrans x day, P<0.003). Percentage of larvae identified as H. contortus decreased in feces collected from lambs treated with COWP and D. flagrans between days 14 and 28 compared with other treatments (COWP x D. flagrans x day, P<0.05). Other trichostrongyles were present and remained less than 7% in feces collected from control lambs. There was no adverse effect of COWP on the ability of D. flagrans to trap residual larvae after COWP treatment. With fewer eggs being excreted due to the effect of copper on H. contortus, and the additional larval reducing effect exerted by the nematode destroying fungus D. flagrans, the expected result would be a much lower larval challenge on pasture when these two tools are used together in a sustainable control strategy.     

Exploring the genetic resistance to natural gastrointestinal nematode infection in Indian goats

The present study investigated the genetic component of host resistance to gastrointestinal nematode infections in two goat breeds in a semi-arid climatic region of India. The study was carried out on 888 animals belonging to two goat breeds. Live weight, faecal egg counts (FEC) and packed cell volume (PCV) following natural parasite challenge were measured at 3, 6, 9 and 12 months of age over a 3-year period. Pedigree relationships between goats extending back 3 generations were available. The study estimated the heritabilities of indicator traits (FEC and PCV) in goats and also quantified relationships between indicator traits and growth traits at the genetic, phenotypic and environmental level. It also provided an insight for the inclusion of genetic information on resistance to nematode infection into breeding programmes. The heritabilities of the indicator traits were low to moderate in this population. Genetic correlations between FEC at 6, 9 and 12 months of age were strong (approaching unity) indicating that the trait may be controlled by same genes at these different ages. The genetic correlation between FEC and PCV from 6 months of age onwards was negative and moderate to strong. Correlations between FEC and growth traits tended to be negative. Selection index modeling investigated the use of FEC, PCV and bodyweight in selection schemes. Selection based on the measurements at 9 months of age was proposed as a means of improving productivity as well as reducing pasture contamination, thereby enhancing sustainable livestock production.     

Dietary impacts on the resistance of Merino lambs to Trichostrongylus colubriformis

AIM: To evaluate and compare the effects of a variety of diets on the resistance of young, lightweight Merino lambs to repeated low-dose infections of Trichostrongylus colubriformis.

METHODS: Ninety-six 12-week-old lambs were fed balanced or unbalanced diets, and given primary (at 19 weeks of age) or both primary (at 12 weeks) and secondary (at 19 weeks) infections of T. colubriformis. Suboptimal diets were low in total intake, rumen undegradable protein, total protein, readily available carbohydrate or minerals, or supplemented with cod liver oil. Liveweight was monitored fortnightly, protection was assessed from worm counts at the end of the study (25 weeks) and faecal nematode egg counts (FEC) conducted weekly, and mast-cell response assessed at the conclusion of the study from concentration of mast-cell protease in the jejunum. Concentrations of glucose in plasma were measured at 21 weeks.

RESULTS: Diets unbalanced for total protein, readily available carbohydrate, Mo or cod liver oil each increased the worm counts after 6 weeks of secondary infection (at 25 weeks of age) and FEC during secondary infection. Low intake of a highnutrient diet restricted liveweight gain but did not affect the development of resistance, as indicated by worm counts and FEC. Defi ciency of available carbohydrate resulted in reduced liveweight gain and reduced concentration of glucose in plasma. There was a reduction in jejunal mast-cell protease concentration in sheep fed unbalanced rations.

CONCLUSIONS: The parasitology results and reduction in the concentration of jejunal mast-cell protease observed in sheep fed unbalanced rations suggest that the nutrient defi ciencies and the fi sh-oil supplement may have acted via inhibition or retardation of the host's acquired immune response. Diets unbalanced for a range of components adversely affected the acquired protective response to T. colubriformis to a similar extent and appeared to involve a similar mechanism as each other. The quality of the diet was more important than quantity for the development of resistance, and soluble carbohydrate was an essential component.     

Garlic and papaya lack control over gastrointestinal nematodes in goats and lambs

Gastrointestinal nematodes (GIN) continue to hinder small ruminant production because of anthelmintic resistance and lack of effective products for GIN control in organic production. The objective of this study was to examine the effectiveness of a commercially available certified organic garlic product, fresh garlic juice, or garlic bulbs as an anthelmintic to control GIN in goats and papaya seeds for GIN control in lambs. In the first experiment, weaned meat goat kids were administered water or a commercial garlic juice product (n = 7/treatment). In the second experiment, kids were administered water, fresh garlic juice, or fed garlic bulbs (n = 9 or 10/treatment). In a third experiment, lambs were administered nothing or papaya seed in water (n = 12/treatment). Naturally infected goats were supplemented with bermudagrass hay and corn/soybean supplement in the first experiment or maintained on bermudagrass pasture in the second experiment or lambs grazed mixed grasses in the third. Blood and fecal samples were collected on Days 0, 7, and 14 after administration of treatment to examine changes in blood packed cell volume (PCV) and fecal egg counts (FEC). PCV and FEC were similar by Day 14 between kids treated with a commercial garlic juice and water in the first experiment. Similarly, PCV was not different among treatment groups in the second experiment. FEC of the garlic juice group was lower than the other two groups on Day 0, but was similar among groups by Day 14. Deworming was required in one goat within each treatment group by Day 7 and in three kids in the garlic juice group and two in the garlic bulb group by Day 14. No changes in PCV or FEC were apparent in response to papaya seed compared with untreated lambs. Based on the alternative plant products used in this study, garlic or papaya seed is not recommended as an aid to control GIN in goats or lambs.     

Use of copper oxide wire particles to control gastrointestinal nematodes in goats

The objectives of these experiments were to determine the optimal dose of copper oxide wire particles (COWP) necessary to reduce gastrointestinal nematode (GIN) infection in young and mature goats naturally infected with Haemonchus contortus or a mixed infection and to determine whether the effectiveness could be enhanced through feeding management. Two experiments were conducted during cooler months in Georgia, and 4 experiments were conducted during warmer spring or summer months in Arkansas. Meat goats received 0 up to 10 g of COWP under a variety of management conditions. In all experiments, blood and feces were collected every 3 or 7 d from 6 to 42 d to determine blood packed cell volume (PCV) and fecal egg counts (FEC) to estimate the degree of GIN infection. In mature goats grazing fall pasture, mean FEC of 0 g of COWP-treated goats increased, and those of 4 g of COWP-treated goats remained low on d 0, 7, and 14 (COWP x d, P < 0.03), and FEC decreased on these days (P < 0.001). In 5 and 10 g of COWP-treated goats, PCV increased (P < 0.001), but FEC and PCV remained unchanged over time in control goats. Fecal egg counts were similar among all low doses (0.5, 1, 2, 4 g) of COWP administered to weaned kids for all dates examined (P > 0.10), which were lower on d 7 through 21 (COWP x date, P < 0.05) but similar by d 28, compared with FEC of 0 g of COWP-treated kids. Packed cell volume was lower in 0 g compared with all COWP-treated kids by d 14 (COWP x date, P < 0.05). Feeding management in combination with COWP for GIN control had little effect compared with COWP alone for these short-term studies. In conclusion, a dose of COWP as low as 0.5 g, which was considered optimal to reduce the risk of copper toxicity, was effective in reducing FEC in young goats, and 5 g of COWP was effective in older goats. Copper oxide does not appear to be effective in controlling newly acquired L4 stage (preadult) larvae, which also feed on blood, leading to decreased PCV in newly infected goats.     

Response of Nkedi Zebu and Ankole cattle to tick infestation and natural tick-borne,helminth and trypanosome infections in Uganda

A cross-sectional study was conducted in Soroti district of Uganda to establish important traits of Nkedi Zebu and Ankole cattle regarding their production performance responses to natural infections of trypanosomes, gastrointestinal nematodes, Theileria parva, Babesia bigemina, Anaplasma marginale and tick infestations. Over four visits between October 2006 to August 2007, tick counts were performed and blood, faecal samples and sera were collected from the Nkedi Zebu (295) and Ankole (165) cattle from 86 herds in six locations per visit. Low parasitological prevalence of trypanosome infection (<6%) and high prevalence of gastrointestinal nematode infections (>30%) with low faecal egg counts (110–300 eggs per gramme (EPG)) were observed in the Nkedi Zebu and Ankole cattle. Both breeds had high, moderate and low mean counts of Rhipicephalus appendiculatus (18.0–24.0), Rhipecephalus (Boophilus) decoloratus (3.6–10.3) and Amblyomma variegatum ticks (1.7–4.3), respectively. In addition, both breeds had similar mean packed cell volumes (26.4–31.2) and a similar percentage of animals were anaemic (14.5–36.6%). The Nkedi Zebu cattle further had higher mean optical density (OD) values for antibodies against T. parva (1.093–1.445) and A. marginale infections (0.573–0.583), and significantly (P < 0.001) higher mean OD values of antibodies against B. bigemina infections (1.07–2.175) than the Ankole cattle: T. parva (1.030–1.302); A. marginale (0.442–0.603) and B. bigemina infections (0.863–2.154). The Ankole cows produced significantly more (P < 0.001) milk per day (2.68 L) than the Nkedi Zebu cows (1.98 L), and the Ankole oxen had significantly higher (P < 0.05) draught power output (2.57 days/acre) than the Nkedi Zebu oxen (2.93 days/acre). Liveweights of calves aged 0–12 months of both breeds were comparable, suggesting that the Nkedi Zebu and Ankole cattle under similar disease challenge exhibited similar growth rates. In conclusion, the Nkedi Zebu cattle seem to possess a higher degree of disease resistance against endemic parasitic diseases, while the Ankole cattle seem to possess a moderate degree of disease resistance coupled with a moderate production potential.