Results of diagnostic milk samples sent to the wallaceville animal health laboratory

The occurrence of a field strain of Haemonchus contortus resistant to thiophanate is reported for the first time in New Zealand. In a controlled anthelmintic trial with experimentally infected animals, thiophanate at 50–100 mg/kg had no appreciable effect on the Haemonchus burden. Albendazole reduced faecal strongylate egg counts by 95% in animals with naturally acquired infections.     

Critical controlled test to evaluate resistance of field strains of Haemonchus contortus to thiophanate

Following reports of suspected gastrointestinal strongylid nematode resistance to thiophanate in sheep and goats at Sokoine University of Agriculture (SUA), Tanzania, field strains of Haemonchus contortus, one from SUA and another from Kimamba, Tanzania, were selected for a critical controlled test to evaluate the efficacy of thiophanate. The SUA H. contortus strain in goats showed a marked resistance to thiophanate at an oral dose of 50 mg kg-1 liveweight (efficacy = 24.1%), while the Kimamba H. contortus strain showed very marked susceptibility (efficacy = 99.7%) to thiophanate at the same oral dose. This is the first report from East Africa of a field strain of H. contortus resistant to thiophanate. The incidence of resistant strains of strongyloid parasites to benzimidazole anthelmintics in sheep and goats in East Africa is on the increase. The magnitude of this problem should be evaluated and remedial solutions sought.     

The dose response of several benzimidazole anthelmintics against resistant strains of Haemonchus contortus and Trichostrongylus colubriformis selected with thiabendazole

Dose response lines for eight benzimidazole anthelmintics and thiophanate were determined, using standardised strains of thiabendazole selected and resistant Haemonchus contortus and Trichostrongylus colubriformis. Against H contortus, thiophanate, thiabendazole, parbendazole and oxibendazole were inactive. Mebendazole was inactive at dose rates of 6.26 and 12.5 mg/kg, although significant activity occurred at 25 mg/kg. Fenbendazole, cambendazole, oxfendazole and albendazole demonstrated significant activity at dose rates equal to or greater than the recommended therapeutic level. Thiophanate was inactive against resistant T colubriformis. The remaining compounds only showed significant activity when used at dose rates in excess of the recommended therapeutic level. These results show that a side resistance exists among the benzimidazole anthelmintics and suggests that changes in dose response lines could be expected to occur if resistant strains are selected with benzimidazoles other than thiabendazole.     

Multiple Anthelmintic Resistance in Haemonchus Contortus on a Sheep Farm in Kenya

Multiple resistance to albendazole, thiophanate, levamisole and orally administered ivermectin was detected in an isolate of Haemonchus contortus in sheep on a farm where benzimidazole resistance had already been identified. Following a faecal egg count reduction test, this was confirmed by both critical and controlled anthelmintic tests. Different groups of sheep infected naturally or given an experimental infection with the benzimidazole-resistant isolate were treated with the recommended doses of various anthelmintics. Compared to the control group, the percentage reductions in the faecal egg counts of sheep treated with albendazole, thiophanate, levamisole and ivermectin varied between 38.2% and 79.1% and the residual worm counts between 27.3% and 57.5%. The results indicate the presence of multiple anthelmintic resistance in this isolate of H. contortus. Sheep treated with closantel showed 100% reductions in faecal egg and worm counts, indicating that this drug was very effective against the population of H. contortus on the farm.     

Efficacy of thiophanate and albendazole against natural infections of Dicrocoelium dentriticum, Fasciola hepatica, and gastrointestinal nematodes and cestodes in sheep

The anthelmintic efficacy of thiophanate and albendazole was compared in sheep with heavy infestations of Dicrocoelium dentriticum. The effectiveness of each drug was determined by counting the numbers of D. dentriticum in animals killed 21 days after treatment. In one group, the dose of thiophanate recommended for use against gastrointestinal (GI) nematodes (50 mg kg-1 live weight) was found to be 74.4% effective against D. dentriticum. Two tablets (each containing 76 mg of active ingredient) of albendazole per 30 kg live weight were given to a second group and the dose repeated after 1 week. Under this regime, albendazole was found to be 12.7% effective against D. dentriticum. The effect of each drug on other parasites was as follows; thiophanate had no effect against Fasciola hepatica or cestodes, while albendazole was 71.5% effective against F. hepatica and 100% effective against cestodes. Both drugs were highly effective against GI nematodes.     

Rumen function and digestion of Merino sheep divergently selected for genetic difference in resistance to Haemonchus contortus

The aim of this experiment was to investigate the effect of Haemonchus contortus infection on rumen function and digestion of Merino sheep from lines divergently selected for genetic resistance to H. contortus. Rumen function and whole-tract digestibility were determined in 29 Merino weaner wethers from the CSIRO Haemonchus selection flock, increased resistance to Haemonchus (IRH), decreased resistance to Haemonchus (DRH) and random bred control (C) selection lines. Wethers were fed a restricted low quality roughage diet (5.9 MJ ME/kg DM, 29 g MP/kg DM) to maintain weight and were either uninfected (NIL) or infected with H. contortus (INF). Measurements were taken at week 7 of infection, while animals were housed in metabolic crates. Animals were then euthanased to determine abomasal worm counts. IRH had significantly lower worm egg count than DRH and C lines however, adult worm and larval counts, though lower in IRH animals, did not differ significantly. DM and OM digestibility and in sacco degradability of IRH and DRH selection lines were greater than C animals. Rumen function of animals from the IRH line was altered in response to H. contortus infection with an increase in fluid outflow and turnover rate and a decrease in propionic acid concentration. These changes may be a component of a greater host resistance and begin to explain the failure of IRH animals to translate lower worm egg count into greater bodyweight gain.     

Seasonal changes and hypobiosis in Haemonchus contortus infection in the West African Dwarf sheep and goats in the Nigerian derived savanna

A survey was conducted in the Nigerian derived savanna (from August 1987 to July 1988) on the seasonal fluctuations in the composition of Haemonchus contortus burden of naturally infected West African Dwarf sheep and goats. During this period 117 abomasa collected from locally slaughtered animals were processed. Male, female as well as immature worms were enumerated. The incidence of Haemonchus infection was high (77.8-100%) with no definite seasonal distinction. There was however, a clear seasonal trend in the worm burden of animals; higher burdens were evident during the rainy rather than the dry season. There was no significant hypobiosis; Haemonchus contortus survived in the host during the unfavourable dry season (November to March) as adults.     

Voluntary feed intake and diet selection of Merino sheep divergently selected for genetic difference in resistance to Haemonchus contortus

This research was designed to determine if divergent selection for resistance to Haemonchus contortus had produced correlated changes in voluntary feed intake and diet selection. Voluntary feed intake, diet selection and production were determined in 54 Merino weaner rams from the CSIRO Haemonchus selection flock, increased resistance to Haemonchus (IRH), decreased resistance to Haemonchus (DRH) and random bred control (C) selection lines. Weaner rams were fed ad libitum either a high (9.2 MJ ME/kg DM, 90 g MP/kg DM) or moderate (6.3 MJ ME/kg DM, 30 g MP/kg DM) quality diet and given the choice between the two diets, when uninfected (NIL) or infected with H. contortus (INF). Symmetrical response to divergent selection for worm egg count (WEC) was not matched by a symmetrical change in feed intake and there was no difference in diet selection between selection lines. Feed intake, growth and wool production of DRH animals remained the same as that of IRH, yet DRH animals had five times greater WEC than IRH. This study begins to explain the mechanisms that allow resistant animals to effectively prevent establishment and/or development of H. contortus, by maintaining a greater immune response to infection through higher circulating eosinophils, plasma globulin and IgG(1) antibody titres. Susceptible animals have displayed resilience by improving feed conversion efficiency and increasing protein synthesis.     

The importance of endoparasite counts at necropsy

In a 2-year study of 49 Oklahoma cattle with a typical history of clinical endoparasitism, 12 animals had Ostertagia only, and Ostertagia was the predominant endoparasite in 21. Only 1 animal had a pure Haemonchus population. Though primary endoparasitism was diagnosed antemortem in 32 animals, postmortem worm counts confirmed the diagnosis in only 19. Worm counts documented inapparent disease in 8 animals. In 21 cases of suspected of toxicosis, 12 animals had endoparasitism none was poisoned.     

T-cell receptor and immunoglobulin gene polymorphisms and resistance to Haemonchus contortus in sheep

SUMMARY: DNA extracted from animals originating from three large half-sib sheep families derived from a single, highly resistant ram were probed with ovine T-cell receptor α and β chain and immunoglobulin lambda light chain variable and constant region cDNA probes. When genomic DNA was digested with TaqI, 19 polymorphic bands were detected with the lambda light chain immunoglobulin variable region probe and 6,4 and 5 polymorphic bands were detected with the T-cell receptor α and β probes and the lambda immunoglobulin constant region probes, respectively. All animals had been phenotypically assessed for Haemonchus contortus resistance by faecal egg counts and using best linear unbiased statistical methods, no statistically significant associations were found between RFLP banding patterns detected at these loci and faecal egg counts. The results show that germline polymorphism at these loci does not account for a significant proportion of the variation in resistance to Haemonchus contortus in this flock. ZUSAMMENFASSUNG: T-Zellrezeptor und Immunoglobulin-Genpolymorphismus und Resistenz von Schafen gegen Haemonchus contortus DNS aus Tieren von drei gro?en Halbgeschwister-Schaffamilien aus einem einzelnen hochgradig resistenten Schafbock wurden mit cDNS-Sonden aus ovinen T-Zellrezeptor α- und β-Ketten und Immunoglobulin λ leichten variablen Ketten und konstanten Regionen untersucht. Nach Verdau der genomischen DNS mit TaqI 19 wurden polymorphe Banden mit der λ leichte Ketten Immunoglobulin variablen Region-Sonde entdeckt, 6, 4 und 5 polymorphe Bande wurden mit T-Zellrezeptor α- und β-Sonden und mit der Sonde der λ Immunoglobulin konstanten Region gefunden. Alle Tiere wurden ph?notypisch in Hinblick auf Haemonchus contortus-Resistenz mittels f?kaler Eiproben untersucht. Statistische Analyse mittels linearer unverzerrter Pr?diktion ergab keine statistisch signifikanten Zusammenh?nge zwischen RFLP Bandmustern und f?kalen Eizahlen. Genetischer Polymorphismus an diesen Loci scheint nicht für einen signifikanten Teil der Variabilit?t in der Resistenz gegen Haemonchus contortus verantwortlich zu sein.     

The seasonal epidemiology of gastrointestinal nematodes in N'Dama cattle in The Gambia

From June 1987 to June 1988, a total of 180 N'Dama cattle were necropsied to identify and enumerate parasites present, including 39 sick calves and 25 dead calves from local village herds, and 116 adult cattle from a local abattoir. Of 175 animals infected with one or more helminths (97%), Haemonchus contortus was found in 67% of all necropsied animals, Cooperia punctata in 75%, Cooperia pectinata in 55%, Oesophagostomum radiatum in 71% and Bunostomum phlebotomum in 21%. There was a wide range of worm burdens (0-22 925) and a pronounced seasonal pattern occurred. Eighty-two percent of the total adult Haemonchus burden occurred during the rainy season (June-October). By the end of the rainy season, almost 100% of the Haemonchus burden was present as inhibited larvae. By contrast, a different survival strategy appeared to occur in Cooperia spp.; Oesophagostomum spp. and Bunostomum spp., which were found as adults throughout the year. Results indicated that, apart from malnutrition during the dry season, gastrointestinal nematode infections, especially haemonchosis, represent a major constraint on the health and productivity of N'Dama cattle under West African savanna conditions.     

Characteristics of helminthic parasitism in cattle in Ituri (Haut-Zaire). II. Parasitic associations

A total of 781 cattle was examined at the Bunia slaughterhouse (Ituri) from August 1986 to December 1987 to study the following parasitic associations: Fasciola sp., Schistosoma sp., paramphistomes and Fasciola sp., Haemonchus sp., Oesophagostomum sp. Prevalences were high for each parasite: 96.5% for paramphistomes, 58.1% for Schistosoma sp., 58.7 to 61.9% for Fasciola sp., 90.5% for Haemonchus sp. and 75.5% for Oesophagostomum sp. Regarding the association with trematodes, 41.3% of the 516 examined animals were simultaneously positive for the three helminths and there was a significant relationship between the infection with Fasciola sp. and Schistosoma sp. Regarding the association with Fasciola sp., Haemonchus sp. and Oesophagostomum sp., a total of 44.5% of the 265 examined animals harboured the three parasites together, but infections seemed not to be linked. Moreover, the corresponding gross lesions were moderate suggesting a low level of the parasitic burdens.     

Changes in liveweight gain and blood constituents in experimental infection of goats with a goat-derived compared with a sheep-derived strain of Haemonchus contortus.

Two groups of goats were experimentally infected with two different strains of Haemonchus contortus and compared with the controls. Group A animals were infected with a goat-derived strain (GDS) while Group B animals were infected with a sheep-derived strain (SDS). Changes in the liveweights and some blood constitutents between the two infected groups were compared. The pathogenic effects of the GDS larvae were generally more serious when compared with those of the SDS larvae.     

Resistance of nematode eggs to the ovicidal activity of benzimidazoles

Eggs of benzimidazole-resistant Haemonchus contortus and Trichostrongylus colubriformis are resistant to the ovicidal activity of benzimidazoles. The possiblity is raised of using this as a simple screen for detection of resistance in nematodes of domesticated animals.     

Prevalence of <Emphasis Type="Italic">Haemonchus contortus</Emphasis> infection in sheep slaughtered at Jimma town municipal abattoir,Ethiopia

Haemonchus contortus is a parasite of major economic importance of most sheep-rearing areas of the world. A cross-sectional study was conducted from November 2015 to March 2016 with objectives of determining the prevalence and associated risk factors of Haemonchus contortus infection in sheep slaughtered at Jimma town municipal abattoir, Ethiopia. Of the total 7000 sheep slaughtered during the study time period, 384 sheep were randomly selected and examined for parasites. The overall prevalence of Haemonchus contortus infection was 264 (68.75%). Infection rate of poor body condition animals was significantly (P?=?0.000) higher than good body conditioned animals. The mean packed cell volume (PCV) values (%) of parasitemic and aparasitemic sheep were 23.73?±?3.7 SD and 37.66?±?4.736 SD, respectively. The prevalence in adult sheep (>?1 year) was insignificantly (P?=?0.653) higher than that of young sheep (≤?1 year). The highest prevalence was recorded in sheep that originated from Seka district (73.3%) and the lowest in Kersa district (63.4%) with non-significant variation (P?=?0.691). The highest monthly mean worm burdens and prevalence of Haemonchus contortus infection were recorded in November and lowest in March. The current study revealed that Haemonchus contortus infection is an important and common parasitic disease and requires special attention to its control.     

Experimental infection of sheep by the camel stomach worm, Haemonchus longistipes

An attempt has been made to infect sheep by Haemonchus longistipes with the objective of developing a relatively cheap and manageable model of camel haemonchosis. A large proportion of inoculated animals (28/34) developed patent infections; the prepatent period was short, lasting for 3 to 4 weeks in the majority of infected animals. Worm burdens were low and so was the total egg output. Most of the recovered worms were reduced in size.     

The relation of climate and topography to worm egg counts of gastro-intestinal nematodes of sheep in the Eastern Cape

Haemonchus, Trichostrongylus, Ostertagia and Nematodirus worm populations of sheep based on differential egg counts are considered in relation to climatological and topographical data. Late spring, summer and early autumn rainfalls are related to ground slope to assess wetness. Egg counts indicated that the estimated worm populations in animals in flat areas with low rainfall were as heavy as or heavier than in animals on steep hilly areas with a high rainfall. It is proposed that tactical anthelmintic treatment be based on the degree of wetness of the grazing or farm.     

Nematode parasitism in adult dairy cows in Belgium

Over a period of 1 year, from November 1997 to October 1998, the abomasa, blood and faecal samples of 121 dairy cows in Belgium were collected and examined for nematode infections. Nematodes were present in the abomasa of 110 animals. Ostertagia was found in all 110, Trichostrongylus was seen in 65 and Haemonchus in 14 abomasa. Overall, 91% of all trichostrongyles recovered were Ostertagia. The geometric mean total number of Ostertagia was 2750, with an average of 74% inhibited early fourth stage larvae (EL4). Between November and February >90% of the Ostertagia worm burden were EL4 stages. The majority of the animals (56%) harboured a low Ostertagia burden (100-5000) and 15% had a high burden (>10,000). Sixty-four percent of the coprocultures were positive and the genera recovered were Ostertagia sp. (100%), Trichostrongylus sp. (42%), Oesophagostomum (32%), Haemonchus sp. (29%) and Cooperia sp. (16%). A seasonal pattern was evident for serum Ostertagia-specific antibodies and for serum pepsinogen concentration, with the highest levels during the summer, and low values during the winter. Dictyocaulus viviparus specific antibodies were detected in the serum of eight (7%) animals.     

甲基托布津对野大麦内生真菌共生体的生长及生理生化的影响

以我国北方优良耐盐牧草野大麦(Hordeum brevisubulatum)为研究对象,进行了杀菌剂甲基托布津对野大麦内生真菌共生体的生长及生理生化影响的研究。结果表明,甲基托布津稀释500倍浸泡种子8 h后播种,出苗率显著降低(P0.05),从85%降至72%,幼苗带菌率显著降低(P0.05),由100%降至12%;杀菌剂处理可降低野大麦的株高、分蘖,但对其叶绿素含量、丙二醛含量、脯氨酸含量、过氧化氢酶活性、过氧化物酶活性和超氧化物酶活性均未产生显著影响(P0.05);杀菌剂处理后野大麦的C、N、P含量较蒸馏水浸种对照分别显著降低了4.87%、10.99%、13.50%(P0.05)。因此,甲基托布津稀释500倍浸泡种子8 h为去除野大麦种传内生真菌的有效办法。     

Haemonchus contortus resistance to ivermectin and netobimin in Brazilian sheep.

Suffolk, Texel, Hampshire Down and Ile de France sheep from the municipalities of Porto Amazonas, Piraquara and Araucaria in the State of Paraná, and Bagé in the State of Rio Grande do Sul were brought to Sobral, State of Ceará, to be used in a cross-breeding project. On arrival they had clinical signs of nematode parasitosis, and one Suffolk female died. The animals were treated orally with ivermectin (0.2 mg kg-1) and fifteen days later with netobimin (20.0 mg kg-1). Neither drug reduced the egg counts (measured in eggs per gram, EPG) significantly, and this suggested that the nematodes in the sheep were resistant to the anthelmintics used. Haemonchus contortus was the species involved. The egg counts were reduced after oral treatment with trichlorfon (100.0 mg kg-1). Haemonchus contortus larvae obtained from these animals before trichlorfon treatment and passaged through two nematode-free sheep were used in a further experiment. Twenty 6- to 9-month-old nematode-free lambs were infected with the H. contortus larvae (10,000 per animal) and after the infection was confirmed, were randomly divided into four groups of five animals. Group I was orally treated with ivermectin at 0.2 mg kg-1, Group II with oral netobimin at 20.0 mg kg-1, Group III with oral trichlorfon at 100.0 mg kg-1 and Group IV was a non-treated control. Egg counts and faecal cultures were taken before dosing on the day of treatment and seven days later when all animals were necropsied and the nematodes were collected from the abomasa and counted.(ABSTRACT TRUNCATED AT 250 WORDS)