Molecular detection of Theileria spp. in sheep and vector ticks in the North Khorasan Province, Iran

A survey was carried in North Khorasan Province, Iran in 2010–2011, designed to identify Theileria spp. infections of both sheep and ticks. The tick species were also examined. Ninety sheep from different flocks were clinically examined, and blood samples and ixodid ticks were collected. Light microscopy of blood smears revealed Theileria spp. infection in 37 (41.1 %), while 74 (82.2 %) of blood samples were positive using semi-nested PCR. Theileria ovis, Theileria lestoquardi, and mixed infection were detected in 63/90 (70 %), 5/90 (5.5 %), and 6/90 (6.6 %) of samples, respectively. Of the 434 ticks that were collected, the most prevalent species was Rhipicephalus turanicus (69.3 %) followed by Hyalomma marginatum turanicum (18.4 %), Dermacentor marginatus (6.4 %), and Rhipicephalus bursa (5.7 %). The ticks were separated into 42 tick pools, and the salivary glands were dissected out in 0.85 % (w/v) saline under a stereomicroscope and examined using semi-nested PCR. Three pools of H. marginatum turanicum salivary glands were infected with T. ovis and T. lestoquardi, and one pool of R. turanicus was infected with T. ovis. Based on these results, it is concluded that the prevalence of T. ovis is higher than T. lestoquardi and that H. marginatum turanicum and R. turanicus are likely vectors of T. lestoquardi and T. ovis in this area.     

Gastro-intestinal nematodes of gazelle,Gazella subgutturosa,in Iran

Sixty-five gazelles, Gazella subgutturosa, of different ages and sexes, from different National Parks and Protected Regions of Iran, were examined over a period of 2 years, for gastro-intestinal nematodes. All of the examined animals were infected with one or more nematode species. The following species were found: Marshallagia marshalli, Camelostrongylus mentulatus, Ostertagia occidentalis, O. circumcincta, Trichostrongylus colubriformis, T. vitrinus, Nematodirus gazellae, N. oiratianus, N. spathiger, N. archari, N. abnormalis, N. filicollis, N. sugatini, Nematodirella cameli, N. longissimespiculata, N. antilocaprae, N. gazelli, Skrjabinema ovis, Trichuris ovis, T. gazellae, T. skrjabini and T. discolor. Among the species found, Marshallagia marshalli, Nematodirus spp. and Nematodirella longissimespiculata were the most prevalent helminths.     

Prevalence of gastrointestinal helminths,lungworms and liver fluke in sheep and goats in Norway

The present study describes the occurrence of various gastrointestinal helminths, lungworms and liver flukes in Norwegian sheep and goats as assessed from faecal samples and post mortem examinations performed between 2007 and 2010. Faecal samples for gastrointestinal nematode egg counts were collected from 77 sheep flocks and 30 dairy goat flocks from three geographical regions in Norway. Additionally, thirty-two lambs and 16 adult goats were euthanized for necropsy examination and for identification of adult gastrointestinal nematodes and tapeworms, lungworms and liver flukes. The survey showed that there was a higher mean excretion of trichostrongyle eggs in sheep than in goats at the individual level (392 EPG vs. 154 EPG, p < 0.001). For both host species, the mean prevalence and intensity of excreted trichostrongyle eggs were significantly higher in the southern coastal region compared with the inland and northern regions (p < 0.001). Third stage larvae of Trichostrongylus/Teladorsagia, Haemonchus and Nematodirus type were the most prevalent ones in the coprocultures from sheep, whereas larvae of Trichostrongylus/Teladorsagia and Nematodirus type dominated in goats. The most prevalent gastrointestinal nematode species found at necropsy was Teladorsagia circumcincta (75.0 and 81.2% respectively in sheep and goats), while the largest mean worm burdens were recorded for Haemonchus contortus in sheep (724 ± 623) and T. circumcincta in goats (377 ± 529). Other gastrointestinal nematode species were present at low prevalence or in low numbers.     

Helminth parasites of grysbok, common duikers and Angora and Boer goats in the Valley Bushveld in the eastern Cape Province

Helminth parasites were collected from 13 grysbok, Raphicerus melanotis, 12 common duikers, Sylvicapra grimmia, 24 Angora goats and 24 Boer goats killed on a farm in Valley Bushveld in the eastern Cape Province. Nematodes belonging to 9 species and a further 2 genera and cestodes belonging to 1 species and a further genus were recovered from the grysbok. Of these, worms of the genus Skrjabinema, Trichostrongylus rugatus, Trichostrongylus pietersei and Nematodirus spathiger were the most prevalent and the most numerous. An amended list of the helminths of grysbok is included. Seven nematodes, identified to species and 1 identified to genus were recovered from the common duikers. N. spathiger and Setaria scalprum were the most prevalent, while N. spathiger and Trichostrongylus axei were the most abundant. The Angora goats were infested with at least 10 nematode species and 2 cestodes and the Boer goats with at least 14 nematode species. With the exception of Trichostrongylus pietersei, the Boer goats harboured more nematodes of each species than did the Angora goats. Nematodirus spp. and worms of the genus Skrjabinema were most numerous in Angora goats, and Nematodirus spp. and Teladorsagia circumcincta in the Boer goats. No clear pattern of seasonal abundance was evident for any of the helmith species in the various hosts.     

Endoparasites of brushtail possums (Trichosurus vulpecula) from the South Island,New Zealand

As part of a study to assess whether endoparasites could assist in the biological control of brushtail possums in New Zealand, we investigated the composition and distribution of possum endoparasites in the South Island. Possums were collected near five of the original release areas in the South Island: Banks Peninsula, Hokitika, Nelson, Dunedin and Invercargill.

Among the nematodes, those most frequently encountered were Trichostrongylus spp., which were present in possums from all five study areas. Trichostrongylus species from possums in the Invercargill area comprised 4.5% T. colubriformis, 0.9% T. vitrinus and 11.3% T. retortaeformis. Paraustrostrongylus trichosuri and Parastrongyloides trichosuri were found only in the Invercargill area, where they infected 1.4% and 14% of possums respectively. The cestode Bertiella trichosuri was present in possums from all locations except Dunedin. The protozoan Eimeria spp. occurred in all areas.

These are the first records of Parastrongyloides trichosuri, Paraustrostrongylus trichosuri, T. vitrinus, T. retortaeformis and Eimeria spp. in South Island possums.

The prevalence of endoparasites and the intensity of infection was very low compared to the lower North Island of New Zealand. Endoparasites at the existing levels in the South Island probably have very little effect on possum populations.     

Molecular detection of piroplasms in ixodid ticks infesting cattle and sheep in western Oromia, Ethiopia

In Ethiopia, ticks and tick-borne diseases are widely distributed and contribute to important economic losses. Several studies investigated the prevalence and species composition of ticks infesting ruminants; however, data on tick-borne pathogens are still scarce. During the study period from October 2010 to April 2011, a total of 1,246 adult ticks and 264 nymphs were collected from 267 cattle and 45 sheep in Bako District, western Oromia, Ethiopia. The study showed infestation of 228/267 (85.4 %) cattle and 35/45 (77.8 %) sheep with adult ticks. Overall, eight tick species, belonging to three genera (Amblyomma, Rhipicephalus, Hyalomma), were identified and Amblyomma cohaerens (n?=?577), Rhipicephalus evertsi evertsi (n?=?290), Rhipicephalus (Boophilus) decoloratus (n?=?287), and Amblyomma variegatum (n?=?85) were the more prevalent species. A statistically significant host preference in A. cohaerens for cattle and R. evertsi evertsi for sheep was noticed. Molecular detection of piroplasms, performed only for adult ticks of two species of the genus Rhipicephalus (R. evertsi evertsi and R. decoloratus), revealed an overall prevalence of 4 % (8/202) Theileria buffeli/sergenti/orientalis, 0.5 % (1/202) Theileria velifera, and 2 % (4/202) Theileria ovis. The study showed that tick infestation prevalence is considerably high in both cattle and sheep of the area, but with a low intensity of tick burden and a moderate circulation of mildly pathogenic piroplasm species.     

Development of villus atrophy in the small intestine of sheep infected with Trichostrongylus rugatus

Pairs of sheep infected with 120 000 larvae of Trichostrongylus rugatus were killed at intervals from 2 to 56 days after infection (DAI). Worms were located in tunnels in the epithelium of villi or upper intestinal crypts at all stages of development. Villus atrophy developed progressively until 16 DAI, when surface microtopography, characterised by subtotal villus atrophy, stabilised. Most severe lesions were in the first 3 m of small intestine where the density of nematodes was highest. Discontinuities in the epithelium and effusion of inflammatory cells and tissue fluids into the lumen were rare. No effects of infection on body-weight gain, appetite or serum total protein and albumin were evident in the first 20 days of infection. However, it was concluded that T. rugatus fundamentally resembled T. colubriformis and T. vitrinus in the response it elicited in the intestine of sheep, and must be considered potentially pathogenic.     

Dynamics of the free-living stages of sheep intestinal parasites on pasture in the North Island of New Zealand. 1. Patterns of seasonal development

Abstract

AIM: To describe the seasonal pattern of development of third-stage infective larvae (L3) from eggs of Teladorsagia (=Ostertagia) circumcincta, Trichostrongylus colubriformis and Haemonchus contortus on pasture in the North Island of New Zealand.

METHODS: Sheep faeces containing known numbers of eggs of all three nematode species were deposited on, or buried in, pasture plots at three sites, viz coastal Manawatu, Upper Hutt Valley, and East Cape hill country. Development was measured by recovering L3 from faeces, herbage and soil 28–31 days after deposition on 13–18 occasions, between January 2005 and July 2006. Analysis of the number of larvae recovered used a mixed model including number of eggs deposited, weight of faeces recovered (an assumed indicator of earthworm activity), site, contamination date, and position of deposited faeces, i.e. on the surface or buried.

RESULTS: There was a significant effect of contamination date on development of all three species, with maximum numbers ofL3 developing between late spring (November) and early autumn (March), and minimum numbers in June and July. There were large differences between species, with H. contortus exhibiting a long period (April to October) where development was close to zero, whereas T. circumcincta developed to some extent all year round. Development of T. colubriformis was intermediate between the other two species.

Burying faeces containing nematode eggs increased the number of L3 recovered compared with surface deposition (p≤0.001), although there were a small number of exceptions involving only T. colubriformis. The weight of faeces recovered at harvest, which was assumed to be an indication of earthworm activity, was correlated with the number of L3 recovered for all species (p<0.001). In a separate analysis, earthworms were assumed tohave been active if <5 g faeces remained at harvest. Where this occurred, the number of L3 of T. colubriformis and T.circumcincta recovered was reduced by 56% and 58%, respectively (p<0.001).

CONCLUSIONS: A marked seasonal pattern of development was observed for all three species, with the most larvae developing in spring-early autumn and the least in winter. This seasonal pattern was most pronounced in H. contortus and least obvious in T. circumcincta. Burying faeces containing eggs generally resulted in more L3 being recovered, whilst the apparent activity of earthworms resulted in fewer larvae being recovered.     

Inhibition of the development of Trichostrongylus spp. as third stage larvae in sheep

In non-lactating Frisian ewes slaughtered in September and November 1975 and in ewes slaughtered in March/April 1976 at lambing, the majority of Trichostrongylus axei, T. vitrinus and T. colubriformis found were inhibited third stage larvae (L₃). However, some larvae at various stages of development were found in the animals slaughtered at lambing. In contrast, in lactating ewes slaughtered 6 weeks after lambing in April 1976, almost all Trichostrongylus spp. appeared to be adults. All ewes grazed a pasture heavily contaminated with gastro-intestinal nematodes from June 1975 until at least 2 weeks before necropsy.In lambs on the pasture from April or June 1975, and slaughtered in September and November 1975 and March 1976 after at least 2 weeks of isolation, only small proportions of the Trichostrongylus spp. populations appeared to be L₃. Similar results were obtained from tracer lambs kept at pasture from August 1975 to March 1976. The implications of these findings are discussed.     

Gastrointestinal Nematodes in Indigenous Zebu Cattle under Pastoral and Nomadic Management Systems in the Lower Plain of the Southern Highlands of Tanzania

This study aimed to determine the prevalence and intensity of gastrointestinal nematode infections in indigenous Zebu cattle in the lower plain (lowland zone) of the southern highlands of Tanzania. Gastrointestinal tracts were randomly purchased at the Iringa regional abattoir and at Kihesa and Ipogolo slaughter slabs in different seasons of the year. The contents of the abomasum, small intestine and large intestine were processed separately to recover the worms. The results indicated that 140 out of 144 (97.2%) of the examined animals were infected. The mean (±SE) total worm burden was 1284±183 (range 10–12 600) worms per animal and most infected animals contained more than one nematode species. The nematode species present, their prevalence and mean burden were as follows: Haemonchus placei, 84.7%, 316; H. similis, 5.6%, 1; Oesophagostomum radiatum, 79.2%, 66; Cooperia pectinata, 55.6%, 713; C. punctata, 44.4%, 157; Bunostomum phlebotomum, 5.6%, 5; Trichuris globulosa, 5.6%, 2; and Trichostrongylus colubriformis, 1.4%, 24. The burdens were mainly composed of Cooperia pectinata (55.5%), Haemonchus placei (24.6%), Cooperia punctata (12.3%) and Oesophagostomum radiatum (5.1%). The highest burdens occurred at the end of the rainy/early dry season, while the lowest burdens were found at the end of the dry/early rainy season. There was no difference in the burdens between male and female animals. Immature cattle (<3 years) had significantly higher worm burdens than mature cattle (p<0.01). A poor grade for a live animal was associated with higher worm burdens only in immature cattle and then especially during the dry season (r = 0.456, p<0.001). Anthelmintic treatments in the late rainy/early dry season and early rainy season are recommended in order to prevent outbreaks of helminthosis during the dry season and to reduce carryover of infection into the next rainy season. An additional wet season treatment is advisable in immature cattle, but may not be needed for mature cattle owing to the availability of plenty of mature, good quality pasture.     

Serum concentration of sialic acids in naturally occurring ovine babesiosis

This study is designated to assess the effect of the severity of Babesia ovis infection on sialic acid concentration in blood sera in naturally infected sheep. Infected animals (diseased group) comprised 38 Iranian fat-tailed sheep, about 1–3 years old, naturally infected with B. ovis, divided into four subgroups with respect to parasitemia rates (low 0.1–0.3 %, moderate 0.4–0.9 %, high 1–2.5 %, and very high >2.5 %). The parasitological diagnosis was confirmed using PCR analysis. As a control group, ten clinically healthy sheep reared under the same management and environmental conditions were also sampled. Hematological parameters and the concentrations of total sialic acid (TSA), lipid-bound sialic acid (LBSA), and protein-bound sialic acid (PBSA) were measured in both groups. Compared to controls, sialic acid concentrations showed significant increase (p?Parasitemia rate was positively correlated with sialic acid concentrations. This study demonstrated that B. ovis infection induced marked and persistent elevations of serum sialic acid concentrations. It seems that increase of serum sialic acid concentrations during parasitemia alter receptor-ligand interactions, which are known to play important role in immune response. Furthermore, sialic acid would indirectly inhibit the action of leukocytes and consequently promote the evasion of the immune response and persistence of the parasite in the host. This factor could influence the parasite-host cell adhesion, but further detailed biochemical investigations are needed to precisely explain the exact role of sialic acid in invasion process of the parasite to the host cells.     

Helminths in camels in Iraq

Summary Twenty-five camels (Camelus dromedarius) were examined at Baghdad City abattoir. Of the 13 helminth species recorded,Trichostrongylus spp. were the most common, whileCamelostrongylus mentulatus and the hydatid larval cysts ofEchinococcus granulosus were also frequently found.Cooperia oncophora, Cooperia memasteri were recorded for the first time in Iraq.     

Multiple anthelmintic resistance and the possible contributory factors in Beetal goats in an irrigated area (Pakistan)

This paper presents the first report of multiple anthelmintic resistance in the gastrointestinal nematodes of goats and its possible contributory factors in an irrigated area (Pakistan). A total of 18 privately owned Beetal goat flocks were selected in order to determine the anthelmintic resistance against commonly used anthelmintics. Forty to 48 animals from each flock were selected according to their weight and egg count. The three anthelmintics viz., oxfendazole, levamisole and ivermectin, were given to three groups at manufacturer’s recommended dose while one group was kept as untreated control. Anthelmintic resistance was determined through faecal egg count reduction and egg hatch tests while assessment of the contributory factors of anthelmintic resistance was measured through the rural participatory approach. Faecal egg count reduction test revealed high prevalence of anthelmintic resistance (83.3%) and it was either single (levamisole) or multiple (oxfendazole and levamisole). Egg hatch test confirmed the resistance against oxfendazole as detected with faecal egg count reduction test. None of the goat flocks was resistant to ivermectin. Copro-cultures revealed that Haemonchus contortus, Trichostrongylus colubriformis and Teladorsagia circumcincta were the most common species exhibiting resistance to levamisole and oxfendazole. Step-wise logistic regression of the data on worm control practices revealed significant role of under-dosing, low-protein diets, healthcare supervision by the traditional healers and mass treatments.     

Dual infection of lambs with Trichostrongylus colubriformis and chlamydiae

Lambs in one group were inoculated with chlamydiae and Trichostrongylus colubriformis larvae simultaneously; lambs in a second group were inoculated with chlamydiae after a T. colubriformis infection was established. Results were compared to those from groups inoculated with T. colubriformis only and chlamydiae only. There were no significant differences in fecundity associated with chlamydial inoculation. Packed cell volumes (PCVs) were depressed in groups inoculated with chlamydiae, and chlamydial antibody formation appeared to be inhibited when chlamydiae was superimposed on a T. colubriformis infection. Relatively few T. colubriformis adults were recovered in lambs inoculated with chlamydiae and T. colubriformis simultaneously.     

Development and spatial distribution of the free-living stages of Teladorsagia circumcincta and Trichostrongylus colubriformis on pasture: A pilot study

Abstract

AIMS: To measure the development of Teladorsagia (=Ostertagia) circumcincta and Trichostrongylus colubriformis eggs to third-stage infective larvae (L3) at different times of the year. Also, to measure the spatial distribution of L3 across herbage, soil and faeces, in order to assess whether spatial issues could be important in larval dynamics on pasture.

METHODS: Field plots were contaminated with sheep faeces containing approximately 20,000 eggs of each of T. circumcincta and T. colubriformis on five separate occasions, viz 01 December 1996 (summer), 18 March 1998 (autumn), 17 June 1998 (winter), 15 October 1998 (spring), and 23 July 1999 (winter). Replicate plots (n=10) were harvested at intervals for up to 12 months after deposition of faeces, and the number and distribution of L3 were measured. Larvae were sampled from faeces (where these remained), herbage, and three soil zones to a depth of 145 mm.

RESULTS: There were large differences between contamination dates in the percentage of eggs that developed to L3. For both species the highest percentage development was for eggs deposited in December (7.8% and 25.9% for T. circumcincta and T. colubriformis, respectively) and the lowest for June (0.4% and 0.03% T. circumcincta and T. colubriformis, respectively). Development in winter was often delayed, and this was always associated with a low yield of larvae, probably due to compounding mortalities associated with long periods of exposure to low temperatures.

The relative distribution of L3 present on herbage, in faeces or in the soil varied between sampling times. However, overall the most L3 were recovered from soil (74% and 66% for T.circumcincta and T. colubriformis, respectively, averaged over all samples), and the lowest recoveries were from the herbage.

CONCLUSIONS: Although the data are limited, the results indicated that the highest percentage of eggs developed to infective larvae in summer and only minimal development occurred in winter. The data do not support the view that substantial contamination of pastures with sheep parasites occurs over winter. Large numbers of larvae were recovered from soil, which indicates that, assuming they can subsequently migrate onto herbage, soil is a potentially important reservoir ofinfective larvae in New Zealand. Therefore, the spatial distribution of L3 on pasture may affect both the dynamics and transmission of parasite populations. Further work on both these issues is warranted.     

The anthelmintic efficacy of ivermectin in experimentally infected cattle

The 22,23-dihydro derivative (ivermectin) of the major B₁ components of the avermectins was evaluated, by oral and parenteral routes, for anthelmintic activity in cattle experimentally infected with 7 gastro-intestinal nematode species and lungworm. Treatment at three dosage levels was administered when the parasites were in the L₄ developmental stage or when adult. The dosage expected to remove 95% of the nematodes (ED₉₅) by each route of administration against the various developmental stages of each species of parasite was calculated by methods of linear regression to choose dose levels to be used in subsequent developmental field trials. Parenterally, efficacy against L₄ stages of Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, T. colubriformis, Cooperia oncophora, C. punctata, Oesophagostomum radiatum and Dictyocaulus viviparus exceeded 99% with treatment at 0.2 mg ivermectin/kg. Parenteral treatment of the adult parasites resulted in at least 98% reduction of worm burdens, except $\text{? 90\%}$ for T. colubriformis, with 0.2 mg/kg. Oral treatment of L₄ stages of development with 0.2 mg/kg resulted in at least a 95% reduction in worm burdens of each of the 8 species of parasite. Oral treatment of the adult worms with 0.1 mg ivermectin/kg produced at least a 98% decrease in each parasite species, except for T. colubriformis (90% reduction) for which dose-response calculations suggest 95% efficacy with oral treatment at 0.2 mg/kg.     

Nutritional sensitivity of resistance to Trichostrongylus colubriformis in lactating ewes

It has been suggested that the periparturient breakdown of immunity to parasites has a nutritional basis. Our overall hypothesis is that it results from a prioritized scarce metabolizable protein (MP) allocation to reproductive functions (e.g. milk production) rather than to immune functions. We have earlier shown that the relationship between MP supply, milk production and resistance to the abomasal nematode Teladorsagia circumcincta provides support for this hypothesis. Because nutritional sensitivity of resistance to parasites may differ between parasite species, we used the same nutritional protocol to test the overall hypothesis with a different parasite. Thus, five levels of dietary MP, ranging from 0.60 to 1.2 times assumed requirements, were offered for 4 weeks post-parturition to twin-rearing Greyface ewes, experimentally infected with the small intestinal nematode Trichostrongylus colubriformis. We hypothesized that the initial increments of MP supply would increase milk production without affecting the degree of breakdown of immunity whilst later increments would reduce the degree of breakdown of immunity. Indeed, the data suggest that the first two increments of MP supply increased milk production, whilst final worm burdens were reduced from the second increment onwards. MP supply did not affect mucosal mast cell concentration but increased globule leukocyte concentration. These results support the overall hypothesis that scarce MP allocation is prioritized to milk production over immune functions. In addition, the contrast between effects of MP supply on resistance to T. colubriformis and to T. circumcincta supports the view that periparturient immunity to small intestinal nematodes may be less sensitive to nutrient scarcity than periparturient immunity to abomasal nematodes.     

Helminths in a giraffe (Giraffa camelopardalis xgiraffa) from a zoo in Spain

A pregnant female Cape giraffe (Giraffa camelopardalis giraffa) died from an unknown cause in the Aitana Zoo, Alicante, Spain. Neither clinical signs nor macroscopic lesions were observed at necropsy. The alimentary tract was removed and examined for parasites. A total of 2 724 nematodes were found, including Camelostrongylus mentulatus, Trichostrongylus axei, Ostertagia ostertagi, Teladorsagia circumcincta, Teladorsagia trifurcata, Marshallagia marshalli, Trichostrongylus vitrinus, Trichostrongylus colubriformis, Spiculopteragia asymmetrica and Trichuris giraffae. Only T. giraffae and C. mentulatus have been previously reported from giraffes. The other nematodes are common in mouflons, fallow and red deer, which can usually be found in the same paddock as the giraffes in Aitana Zoo. Although its occurrence is unusual in this host, C. mentulatus was the most abundant nematode in our giraffe. This parasite has been related to disease, and even death, in several wild ruminants.     

A comprehensive evaluation and first molecular report of Theileria ovis infection in small ruminants in Saudi Arabia

A total of 1000 clinically healthy small ruminants comprising 500 sheep and 500 goats from five districts within Riyadh Province in Saudi Arabia were investigated by routine Giemsa staining for hematozoan parasites. Out of these, 100 sheep and 95 goat samples were investigated by PCR using three pairs of hemoprotozoan-specific primers. Based on microscopic examination, 33.2% of sheep and 25.2% of goats were found infected with hemoprotozoan parasites, while PCR detected hematozoan infection in 46% of sheep and 33.7% of goats. Extensive molecular characterization of hematozoan infection using six pairs of species-specific primers revealed the dominance of Theileria ovis, rather than any other species, which is recorded for the first time in small ruminants in Saudi Arabia. Prevalence of T. ovis in sheep and goats was found to be the highest in Riyadh (32, 48%) followed by AL-Kharj (31, 35%), Ad-Dawadimi (31, 33%), AL-Majmaah (15, 27%), and Rumah (17, 23%). The highest parasite prevalence was recorded in the 3 years of age and >?4 years of age ruminants, while the lowest prevalence was recorded in <?1 year of age ruminants. No noticeable differences in parasite prevalence between male or female ruminants were recorded. Partial sequencing of 18S rRNA gene revealed the infection of the studied ruminants with four new isolates of T. ovis. Further characterization of the pathogenicity and the clinical effects of these T. ovis isolates in sheep and goats is highly needed. The current results can be helpful in protecting and improving livestock industry in the countries that depend on a high number of small ruminants.

     

Dynamics of the free-living stages of sheep intestinal parasites on pasture in the North Island of New Zealand. 2. Weather variables associated with development

Abstract

AIM: To identify weather variables associated with the development of eggs of Teladorsagia (=Ostertagia) circumcincta, Trichostrongylus colubriformis and Haemonchus contortus to third-stage infective larvae (L3) under a range of climatic conditions on pasture in the North Island of New Zealand.

METHODS: Sheep faeces containing known numbers of eggs of all three nematode species were deposited on, or buried in, pasture plots at three sites, viz coastal Manawatu, Upper Hutt Valley, and East Cape hill country. Development was measured by recovering L3 from faeces, herbage and soil 28–31 days after deposition, on 13–18 occasions between January 2005 until July 2006. Weather data were recorded at each site, and the association between weather variables and number of L3 recovered was analysed using subsets regression to select best-fitting models from several candidate variables, after adjustment for efficiency of recovery of L3. A multiple linear regression model was then developed for each species, to select weather variables that had both significant and substantive effects on the number of L3 recovered.

RESULTS: For all species, mean daily temperature was the bestpredictor of the number of L3 recovered (p=0.001). For T.circumcincta the final model included mean daily temperature and soil temperature (R²=51%), and for T. colubriformis the model only included mean daily temperature (R²=55%). For development of H. contortus, mean daily temperature was the most significant variable, but moisture in the form of rainfall entropy, i.e. the temporal distribution of rainfall, overthe first 14 days was also significant in the final model (R²=34%).

CONCLUSIONS: Temperature was the most important determinant of developmental success of free-living nematodes on pasture at the study sites, and probably also for other parts ofNew Zealand with similar climates. Moisture was not significant in the development of T. circumcincta or T.colubriformis, implying that under the generally moist temperate climate in New Zealand, moisture is seldom limiting for development of these species. Haemonchus contortusappeared to be sensitive to moisture availability and precipitation in the first 14 days after deposition of faeces. The results of this study will be further developed as part of species-specific climate-driven models of parasite development in New Zealand.