Variability of resistance in goats infected with Haemonchus contortus in Brazil

The variability between and within breeds with respect to nematode egg counts (EPG), packed cell volume (PCV) and hemoglobin (Hb) was studied in 36 yearling female goats of the Caninde (15), Bhuj (6) and Anglo-Nubian (15) breeds, exposed to Haemonchus contortus. Nematode-free goats were turned to a contaminated paddock in late February. From then on, fecal egg per gram counts (EPG), packed cell volume (PCV) and hemoglobin (Hb) were determined at 2-week intervals up to Week 18. The EPG, transformed as [log(EPG + 75)], varied (P < 0.01) between goats within breeds and between weeks of exposure, but not between goat breeds (P > 0.05). PCV and Hb were affected by goat breeds (P < 0.05), by goats within breeds (P < 0.01) and by weeks of exposure (P < 0.01). Anglo-Nubians had higher (P < 0.01) PCV and Hb than Caninde; Bhuj had intermediate values. There were two EPG rises; one between Weeks 6 and 10 and the other between Weeks 14 and 16. The within breed variability was marked during the EPG rise on Week 6, when individual egg counts ranged from 130 to 2500. The EPG rises coincided with drops in Hb. PCV presented a similar trend, though not as marked. Haemonchus was responsible for more than 95% of nematode eggs counted. Considering the goat as experimental unit, the correlation coefficients (r) were: -0.45, P = 0.0064, between log(EPG + 75) and PCV; and -0.53, P = 0.0009, between log(EPG + 75) and Hb. The negative correlation between egg counts and blood values suggested breed differences in PCV and Hb were related to resistance to H. contortus infection and/or to its effects.     

The establishment and development of Haemonchus contortus in goats

Twelve goats were inoculated with 40,000 third-stage Haemonchus contortus larvae and two were killed on each of Days 4, 7, 11, 14, 18 and 21 after inoculation (DAI). The number of worms that established, and the site of development were recorded. More worms established in the fundic, than in the middle or pyloric thirds of the abomasum. Early development occurred within the mucosa; emergence into the lumen started between 7 and 11 days after infection. By 4 DAI, all worms had completed the third moult to the L4 stage. At 11 DAI the majority of the worms were adults. A mean of 13.2% of the female worms had eggs in their uteri at 18 DAI; by 21 DAI more than half of the female worms had eggs in their uteri. The development of H. contortus was essentially similar to that described in sheep.     

捻转血矛线虫重组H11抗原山羊免疫保护性试验

以重组H11-1、H11-2及H11-1与H11-2混合物分别免疫山羊后,ELISA检测发现血清抗体均在首次免疫后14 d达到较高水平,在第2次免疫后10 d达到高峰。用10 000只捻转血矛线虫第3期幼虫攻击山羊后,对不同免疫组山羊排出虫卵数、虫卵孵化率和成虫数的统计分析结果表明,免疫组与对照组间差异不显著,但免疫组雌虫数显著少于对照组,这对防治捻转血矛线虫病可能会起一定的作用。     

Effects of condensed tannins on goats experimentally infected with Haemonchus contortus

Although the use of tanniferous plants or condensed tannins as an alternative to anthelmintics to control gastrointestinal nematodes has been largely documented in sheep, studies remain scarce in goats. The objective of this study was therefore to assess the possible impact of condensed tannins in goats infected with adult Haemonchus contortus. Two groups of cull goats were experimentally infected with 10.000 L3 of H. contortus. After 4 weeks, quebracho extracts, representing 5% of the diet DM, were administered for 8 days to one of the two groups. Goats of the second group remained as controls. One week after the end of quebracho administration, the goats were euthanised. Individual egg excretion and pathophysiological parameters were measured weekly during the study. At the end of the study, worm counts were assessed and histological samples from the abomasa were taken to count the numbers of mucosal mast cells, globule leukocytes and eosinophils. The administration of tannins was associated with a significant decrease in egg excretion, which persisted until the end of experiment. This reduction was not associated with any difference in worm number but with a significant decrease in female fecundity. No significant changes in the mucosal density of the three inflammatory cell types were detected between the two groups. These results indicate that the major consequence of tannin consumption in goats is a reduction in worm fecundity and egg output, which does not seem related to significant changes in the local mucosal response.     

Effect of feeding sericea lespedeza leaf meal in goats experimentally infected with Haemonchus contortus

Effect of sericea lespedeza [SL; Lespedeza cuneata (Dum-Cours.) G. Don.] leaf meal feeding was evaluated in two experiments in indoor reared goats with experimental infection of Haemonchus contortus larvae. In the first experiment, ten 8-10 month old male Spanish and Alpine cross kids pair matched for body weight and age were fed SL or bermudagrass [BG; Cynodon dactylon (L.) Pers.] hay one week before infection and were infected with 5000 H. contortus L(3). The animals were maintained on the same diet for the remaining period and were slaughtered 28 days post-infection (DPI) to determine the establishment of incoming infective larvae. Goats fed SL had lower establishment (P<0.05) of H. contortus larvae than that of the control goats fed BG hay. In the second experiment, twenty-five 8-10 months old male Alpine cross, Saanen, Nubian×Saanen and Spanish kids reared in confinement on BG were experimentally infected with 5000 H. contortus L(3). On 35 DPI, the animals were allocated to two groups after blocking by fecal egg count (FEC), and one group was fed SL leaf meal (n=13), and another control group remained on BG (n=12). Four goats/group were slaughtered successively on days 7, 14, and 28 days post SL feeding, except on day 7, when five SL fed goats were slaughtered. Fecal egg counts and blood packed cell volume (PCV) were measured at weekly intervals and worm count, female worm fecundity, worm length and mucosal eosinophils, mast cells and globule leucocytes were measured after slaughter. Goats fed SL had a lower FEC (P<0.05) one week after feeding, as compared to those fed on BG, and the values remained at low level thereafter. Similarly, PCV was also significantly affected by feeding (P<0.01), and feeding and time interaction (P<0.05). However, worm burden, female worm fecundity, parasite length, and mucosal inflammatory cell count were similar between the groups. Feeding SL reduced the establishment of infective larvae and FEC of H. contortus in experimental studies and this plant could be used for biological control of parasite infection under field conditions to limit the harmful effects of the parasites in goats.     

In vivo anthelmintic activity of Phytolacca icosandra against Haemonchus contortus in goats

Two separate controlled and blinded studies were conducted to confirm the dose and non-interference of spinosad and milbemycin oxime (MO) administered orally in combination or alone to dogs for the treatment and control of experimentally induced flea infestations (Ctenocephalides felis) and adult hookworm infections (Ancylostoma caninum). For each study, dogs were allocated randomly based on pre-treatment adult flea and hookworm egg counts to one of four treatment groups of 10 animals each. In each study, spinosad and MO in combination, using the lower half (30-45 mg/kg spinosad; 0.5-0.75 mg/kg MO) of the US commercial dose band (30-60 mg/kg spinosad; 0.5-1.0mg/kg MO) of each active ingredient, or individually alone using the full dose range, were given orally to dogs on Day 0 using a tablet formulation. A placebo control was treated similarly. In one study, on Days -1, 5, 12, 19, 28 and 35 each dog was infested with approximately 100 unfed adult C. felis obtained from the investigator's established flea colony. All dogs were infested via the same method. Forty-eight hour post-infestation flea comb counts were conducted on Days 1, 7, 14, 21, 30 and 37 and were used to determine the knockdown and residual flea activity. In the second study, on Day -27 each of 48 dogs were experimentally inoculated with 100 third-stage infective larvae of the hookworm, A. caninum. Dogs were treated on Day 0 and necropsied on Day 7 or Day 8. All nematodes in the intestinal tract were collected on Day 7 or Day 8, identified and counted by species and stage. Post-treatment, the geometric mean live flea counts were significantly different (p-value<0.0001) between the spinosad/MO combination and the spinosad only treatment groups as compared to the vehicle control group. The flea counts in the MO only group and the control group were not statistically different. The spinosad and MO combination group and the spinosad only treatment group demonstrated significantly different knockdown (100%) and post-treatment residual flea efficacy at Day 30 was 100% for both groups as compared to the vehicle control. The presence of MO in combination with spinosad did not interfere with the flea efficacy of spinosad as compared to the spinosad only group. MO alone did not demonstrate any flea efficacy. Post-treatment, the geometric mean A. caninum worm counts were significantly different (p-value<0.0001) between the spinosad and MO combination group as compared to the vehicle control group. The worm counts in the MO only group and the combination group were not statistically different. The spinosad and MO combination group (99.8% reduction) and the MO only treatment group (99.5% reduction) both demonstrated significantly different hookworm efficacy as compared to the vehicle control group. The presence of spinosad in combination with MO did not interfere with the hookworm efficacy of MO as compared to the MO only group. Spinosad alone did not demonstrate any hookworm efficacy. In summary, flavored spinosad and MO combination tablets administered orally to dogs at the lower end (30-45 mg/kg spinosad; 0.5-0.75 mg/kg MO) of the US commercial tablet unit dose range (30-60 mg/kg spinosad; 0.5-1.0mg/kg MO) were both safe and highly efficacious delivering 100% knockdown and 30 days of residual adult flea control on experimentally infested dogs as well as >99% adult hookworm efficacy evaluated under laboratory conditions. Interference between either drugs was not demonstrated for both of these dose limiting parasites.     

绵阳地区山羊粪便中捻转血矛线虫的分子鉴定

为鉴定绵阳地区山羊粪便中疑似血矛属线虫虫卵的虫种,本研究提取绵阳地区三个县山羊粪便中疑似血矛属线虫的虫卵DNA 60份,采用PCR技术扩增其核糖体第二内转录间隔区(rDNA ITS-2)基因序列,并与GenBank上公布的捻转血矛线虫同源序列进行比较分析。结果显示:60份疑似血矛属线虫的虫卵DNA样品均得到191bp的ITS-2片段;60条ITS-2序列共形成15条不同的序列,含有17个单变异位点,与GenBank中多株捻转血矛线虫的同源性达95.8%~100%;ML系统发育树显示,本研究得到的15种类型ITS-2序列与已报道的捻转血矛线虫(Haemonchus contortus)聚类形成一个分支。综上可得,60份来自山羊的血矛属线虫均为捻转血矛线虫。     

Immunoprotection in goats against Haemonchus contortus after immunization with cysteine protease enriched protein fractions

Haemonchus cysteine proteases, because of their apparent critical function in worm physiology, are considered important candidates in the immunological control of haemonchosis in sheep. Only limited information is, however, available on the immunoprotective properties of these molecules in goats. In the present study cysteine proteases of Haemonchus contortus adult worms isolated from a goat strain (Gran Canaria, Spain) were enriched by affinity chromatography and evaluated as immunoprotective antigens against caprine haemonchosis. The eggs per gram of faeces averaged over the whole experiment for unvaccinated goats (550 +/- 13.5) was significantly greater (P < 0.001) than that of vaccinated goats (61 +/- 2.9). Accordingly, the worm burden was significantly different between the groups (P < 0.05), with mean values of 247.5 +/- 43.8 and 762.5 +/- 78.3 worms per animal in the immunized and nonimmunized goats, respectively. The percentage of egg (89%) and worm (68%) reduction approached those attained with other immunogens used in sheep.     

The response of Nigerian West African Dwarf goats to experimental infections with Haemonchus contortus

One option for controlling haemonchosis in warm pastoral regions is improvement of resistance by selective breeding. Variation in acquired immunity to H. contortus and immunological correlates of infection were studied in West African Dwarf (WAD) goats. Following exposure to 5000 L3, 63 per cent of the inoculum established but 77 per cent of established worms were expelled by week 5. All infected animals were anaemic (day 14). When exposed to 2000L3, 36 per cent of the inoculum was still present (day 35) with no loss by day 49. Persisting primary infection worms survived a superimposed challenge (day 35), but their growth was slowed and resistance to challenge was significant. Most goats showed eosinophilia and parasite-specific IgG responses to primary infection, but only eosinophilia increased after challenge. No consistent associations were found between parasite burden and any immunological measures of infection, but parasite egg counts showed considerable variation. Overall, our results suggest that resistant genotypes exist among the WAD goat population.     

Cross-reactive antigens of Haemonchus contortus adult worms in Teladorsagia circumcincta infected goats.

The adult Haemonchus contortus somatic antigens responsible for cross-reactivity have been analysed using serum samples from goat kids infected and reinfected with Teladorsagia circumcincta. Goat kids infected with T. circumcincta had similar serum ELISA values against somatic antigens of H. contortus as goats infected with H. contortus itself. Immunoblotting confirmed this extensive cross-reactivity particularly in the molecular weight range 105-29 kDa. However, peptides with high (195, 152 and 119 kDa) or low (23 kDa) molecular weight were only faintly recognized by heterologous sera.     

Eprinomectin 'pour-on' and the shedding of Haemonchus contortus eggs in experimentally infected goats

The effect of eprinomectin on goats experimentally infected with the nematode Haemonchus contortus was investigated. Faecal analysis showed that a single dose of eprinomectin 'pour-on' delayed the onset of shedding of eggs for 10 to 17 days.     

Infection of goats with Haemonchus contortus and Trichostrongylus colubriformis: histopathology and pH changes.

Two groups of goats were experimentally infected with Haemonchus contortus and Trichostrongylus colubriformis, and killed at various days after infection (DAI). The percentage of worms that established in the abomasum and the small intestine was low. At necropsy, abomasums from infected goats had thickened walls and oedematous folds. At 7 DAI there was an initial infiltration of eosinophils and some neutrophils which tend to increase with age of infection. The mean pH of the abomasum in goats infected with H. contortus was 5.43 (range 5.3-5.7), while that of the control goats was 3.30 (range 2.8-3.7).     

Effectiveness of copper oxide wire particles for Haemonchus contortus control in sheep

OBJECTIVE: To assess the efficacy of copper oxide wire particles (COWP) for the control of H contortus infections in grazing sheep. PROCEDURE: In experiment 1, 40 worm-free Merino hoggets (11 to 12 months of age) were divided into four equal groups and allocated to separate 0.8 ha pasture plots. Two groups then received 2.5 g COWP whereas the other two groups were untreated. From 1 week after COWP treatment all lambs received a weekly infection of 2000 H contortus larvae. At week 8, six sheep from the untreated group were then allocated to two groups and treated with either 2.5 or 5.0 g of COWP to establish therapeutic efficacy of treatment. Experiment 2 followed a similar protocol but was conducted with 40 worm-free Merino lambs (3 to 4 months of age) and no assessment of therapeutic efficacy was made. Results: In experiment 1 no significant difference in faecal worm egg counts was observed between treatments and faecal worm egg counts remained less than 3000 epg in all animals. Total worm counts were reduced by 37% by COWP treatment (P = 0.055). Both 2.5 g and 5.0 g doses of COWP at 8 weeks of infection reduced faecal worm egg counts by > 85% with the higher dose giving an earlier response to treatment. In experiment 2, faecal worm egg counts at 4 and 6 weeks were reduced by more than 90% in the COWP treated lambs and worm numbers were 54% lower after 6 weeks when all remaining untreated lambs had to be treated for haemonchosis. Mean faecal worm egg counts in the COWP lambs remained below 3500 epg and clinical disease did not develop in the majority of lambs before the end of the experiment at 10 weeks. CONCLUSION: Treatment with COWPs appears to have the potential to reduce establishment and worm fecundity of Haemonchus spp for an extended period and may offer livestock producers a supplementary means of reducing larval contamination of pasture particularly in areas where anthelmintic resistance is a problem and copper supplementation is likely to be beneficial.     

Inheritance of faecal nematode egg count in Barbari goats following natural Haemonchus contortus infection

Genetic parameters for faecal nematode egg count were estimated in naturally infected Barbari goats maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, over a period of 5 years (1999 through 2003). Faecal egg count (FEC) data on 891 records of Barbari goats descended from 69 bucks and 241 does were used in this study. Analyses were carried out by restricted maximum likelihood (REML), fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Three different animal models were fitted. Direct heritability estimates were inflated substantially for this trait when maternal effects were ignored. The direct heritability estimates for the trait ranged from 0.05 to 0.13 depending on the model used. Low (0.04) maternal heritability estimate was observed for this trait in our study. Moderate estimate of the fraction of variance due to maternal permanent environmental effects (c(2)) for faecal egg count (c(2)=0.10) was also observed. Results suggest that direct and permanent environmental maternal effects were important for this trait, however, maternal additive effects had less impact on this trait.     

Effects of Acacia nilotica and Acacia karoo diets on Haemonchus contortus infection in goats

This study was carried out to determine the effects of Acacia karoo and Acacia nilotica diets on Haemonchus contortus infections in goats. Twenty-four Boer goats of mixed sex (live weight 17-22 kg) were randomly assigned to four treatment groups, namely: A. nilotica (AN) group, A. karoo (AK) group, control infected with H. contortus (HC) group and the non-infected control (NHC) group. Animals in the AN, AK and HC groups were orally infected with a single dose of 3000 HC third stage larvae. The AN and AK groups had dried leaves of AN and AK, respectively, included in their basal diet at a rate of 40% dry matter (DM) while the HC and NHC groups had the basal diet throughout the experiment. All animals received a total feed allowance of 500 g DM per day and Katambora Rhodes grass hay ad libitum for roughage. Parameters measured included faecal egg counts and live weight. At the end of the experiment, three animals from each group were slaughtered and abomasal worm burdens were determined. A significant decrease in the faecal egg counts was recorded in animals in the AK group (P<0.05) relative to those in the AN and HC groups. The worm burdens were reduced by 34% in the AK group (P<0.05) and by 10% in the AN group (non-significant) relative to the infected control group. The study indicates that the difference in the effects of the two forages on HC infections may be related to type and concentration of tannins.     

Condensed tannins from Sesbania sesban and Desmodium intortum as a means of Haemonchus contortus control in goats

Two experiments were conducted to determine whether the proanthocyanidin (condensed tannin)-containing forage legumes Desmodium intortum cv Greenleaf and Sesbania sesban (accession 15019) could be integrated into a feeding management strategy as a means of Haemonchus contortus control in goats. The anthelmintic effects of condensed tannin extracts from the two legumes on H. contortus L₃ larvae were studied in an in vitro larval migration inhibition system. The extracts inhibited larval migration in a dose-dependent manner, and at concentrations from 1,000???g/ml condensed tannin, the extract from D. intortum caused a significantly higher inhibition of larval migration than did the corresponding concentrations of the S. sesban extract (P?<?0.01). Prolonged feeding of tanniniferous forage legumes showed that animals receiving D. intortum had the lowest total worm burden, the lowest female to male parasite ratio, the lowest number of eggs in the uterus of each female worm and the lowest per capita fecundity (P?<?0.01). However, there was no change in the performance (weight gain) of parasite-infected goats probably due to incomplete removal of the parasite or prolonged confinement of goats in small pens, which calls for further investigation. However, since there is no single efficient method in control of parasites, based on the obtained data from this experiment, integrated feeding of D. intortum with other suitable method of parasite control is thus suggested.     

Evaluation of copper supplementation to control Haemonchus contortus infections of sheep in Sweden

A pen study was conducted to assess the effect of providing daily copper mineral supplement, or copper wire particle (COWP) capsules, on established or incoming mixed nematode infections in young sheep. For lambs with established (6 week old) infections, COWP resulted in 97% and 56% reduction of the adult and early L4 stages of H. contortus, respectively, compared with controls (p<0.001). Additionally there was a 74% reduction in Teladorsagia circumcincta infections in the COWP lambs compared with controls (p<0.01). However, no effect was observed when COWP were given at the commencement of a larval dosing period of 6 weeks. There was no significant effect of copper mineral supplement (given at the recommended rate to prevent Cu deficiency) on either established, or developing parasite infections. In addition, a field trial was conducted on a commercial farm to assess the effects of COWP in the management of recurrent H. contortus infections, but lack of parasites during the grazing season prevented an adequate assessment from being made. These results indicate that there is little, if any, benefit from a parasite control standpoint in recommending copper therapy, specifically to control parasites in Swedish sheep flocks.