Prevalence of gastrointestinal helminth infections in rodents of Tarai region of Uttarakhand.

The present work was aimed to investigate helminth biodiversity among rodents in order to evaluate the threat for helminth transmission to humans since they act as a potential source of parasitic zoonoses. In this study, faeces of 43 black rats (Rattus rattus) and 35 house mice (Mus musculus) were collected from various habitats viz. domestic places and agricultural fields of different parts of tarai region of Uttarakhand. These faecal samples were examined for the presence of parasitic eggs, adult and segments of the worms. The study revealed that the rodents were infected with 5 genera of helminth parasites, i.e. Hymenolepis nana, Hymenolepis diminuta, Syphacia muris, Capillaria hepatica, Trichuris muris and other strongyle eggs (2 species of cestodes and 4 species of nematodes). Adult Syphacia muris and segments of Hymenolepis nana were also recovered from faecal droppings. Of the 43 samples of black rat, all (100 %) and of the 35 samples of mice 9 (25.71 %) were found positive for one or more than one species of parasitic infections. Greater infection of H. diminuta 19 (44.18 %) followed by H. nana 17 (39.53 %) was seen in rat whereas mice were mostly infected with H. nana. The diversity and prevalence of various parasites reported here within domestic habitats may suggest that these can pose a high risk of helminth transmission to human population and are thus of considerable public health importance.

Esterase profile of Rhipicephalus (Boophilus) microplus populations collected from Northern India exhibiting varied susceptibility to deltamethrin.

Rhipicephalus (Boophilus) microplus is an economically important ectoparasite of cattle. Chemical acaricides remain the most practical method for control of these pests. During past two decades there have been increasing reports of resistance development against synthetic pyrethroids in tick populations of this species throughout the world. A study was conducted to determine the level of susceptibility of R. (B.) microplus to deltamethrin collected from different geographical locations of northern India. LPT bioassay results revealed LC(50) values of deltamethrin ranging from 0.035 to 0.00037 % A.I. Esterase profile of the tick larval extracts using native PAGE, revealed 5 bands of esterase activity designated EST-5 to EST-1A. Inhibitory tests recognized EST-1, EST-2 and EST-3 as Acetylcholinesterases (AchEs), EST-4 and EST-5 as Carboxylesterases (CaEs). The band intensity varied between tick populations of various locations, being more intense in case of the resistant populations. An extra band of esterase activity (EST-1A) was obtained in larval extracts of ticks from 3 locations. This increased esterase activity may be involved in the resistance development in these tick populations. Acaricide resistance is a multi-factorial phenomenon, thus other causes of increased resistance like sodium channel mutation and reduced drug penetration (e.g. cuticle thickening) and behavioural changes (e.g. avoiding the pesticides) are to be tested in future in order to confirm the basic cause of the resistance development in these acaricide resistant tick populations.

Immune responses against recombinant tick antigen, Bm95, for the control of Rhipicephalus (Boophilus) microplus ticks in cattle.

Immune responses against Bm95 recombinant cattle tick antigen and its protective efficacy for control of Rhipicephalus (Boophilus) microplus ticks were determined in experimental crossbred cow calves. Anti-Bm95 antibody titers, as assessed by indirect ELISA, in immunized calves ranged from 196.1+/-13.7 on day 0 to 7979.9+/-312.5 on day 110 post-primary immunization. The rise in antibody titer was statistically significant (p<0.01) throughout the study period. Besides this, constantly higher lymphoproliferative response (LPR), as assessed by lymphocyte stimulation test, was observed from 10 days post-immunization, but a positive LPR of antigen stimulated cells in immunized animals was recorded only on day 50 and day 70 post-immunization. Following challenge of immunized calves with larvae of R. microplus, significant increase (p<0.01) in rejection percentage, mean number of damaged ticks, mean percentage of dead ticks, and decrease in engorgement weight were recorded in immunized animals. Also, there were significant differences (p<0.01) in preoviposition period, oviposition period, egg mass weight and percent hatchability between the immunized and control calves. The percent reduction in number of adult females in vaccinated calves, reduction in mean weight of egg masses, percent reduction in mean weight and reduction in fertility of engorged females collected from vaccinated calves were determined and the efficacy of Bm95 recombinant cattle tick antigen was 81.27%.

The epidemiology of fasciolosis in ruminants in different geo-climatic regions of north India.

Epidemiological studies were conducted on Fasciola giagntica infection in different geo-climatic zones (hills, tarai and plains) in six states of north India during January 2001 to December 2004. Prevalence rates of 10.79, 13.90, 2.78 and 2.35 percent were recorded in cattle, buffaloes, sheep and goats, respectively. Animals in the tarai had the highest prevalence of fasciolosis followed by those in the hills and plains, respectively. The prevalence of infection in cattle and buffaloes was highest during the winters (11.84% cattle, 15.57% buffaloes) followed by summers and rains, respectively. However, the seasonal trends in sheep and goats were the reverse, with the peak prevalence during the rains (4.60% sheep, 2.71% goats). Abattoir studies revealed a higher prevalence in buffaloes (31.14%) than in sheep and goats. Screening of Lymnaea auricularia snails revealed that 5.48% of the snails harboured larval stages of F. gigantica. Also, the snails in the tarai had a higher prevalence (7.28%) of infection compared to those in the plains (1.57%). The results of the present study may help to devise an effective control strategy against fasciolosis in north India.

Genotyping of benzimidazole susceptible and resistant alleles in different populations of Haemonchus contortus from Himalayan and sub-Himalayan regions of North-West India.

An allele-specific PCR was standardized to diagnose the mutation (Phe to Try) at residue 200 of the isotype 1 beta tubulin gene responsible for benzimidazole resistance in Haemonchus contortus adult and infective larvae. Adult and infective larvae of Haemonchus contortus were collected from sheep under different managemental practices (intensive and extensive) in temperate Himalayan regions (Mukteshwar and Kedarkhatta), sub-himalayan region (Pantnagar) of Uttarakhand state and subtropical region of Uttar Pradesh (Bareilly) in north-west India. Genotyping of adult H. contortus, collected from abomasi of slaughtered sheep reared under extensive management, by AS-PCR revealed that the frequency of resistant (r) alleles was significantly higher (P < 0.001) at Pantnagar (0.57) as compared to Bareilly (0.25) and Mukteshwar (0.08). Also, genotyping of infective larvae of the parasite from intensively managed sheep farms indicated that the frequency of resistant (r) alleles was significantly higher (P < 0.001) at Pantnagar (0.85) as compared to Kedarkattha (0.70) and Bareilly (0.62). The results revealed that managemental practices followed in the areas under study have a direct bearing on the spread of benzimidazole resistant alleles.

Duration of anthelmintic effect of three formulations of ivermectin (oral, injectable and pour-on) against multiple anthelmintic-resistant haemonchus contortus in sheep.

We report the results of investigations that were conducted in a sheep flock in Uttaranchal, India where repeated failure of anthelmintic medication was noted. The study revealed that Haemonchus contortus in sheep had developed resistance to benzimidazoles (fenbendazole, mebendazole and albendazole), imidazothiazole (levamisole) and salicylanide (rafoxanide), while it was fully susceptible to avermectins (ivermectin). Further, the suppression of nematode egg output in faeces of sheep naturally infected with multiple anthelmintic-resistant H. contortus following treatment with ivermectin tablet (0.4 mg/kg body weight (bw), orally), ivermectin injection (1% w/v, 0.2 mg/kg bw, subcutaneously) and ivermectin pour-on (0.5 w/v, 0.5 mg/kg bw) was also studied over a period of 10 weeks post treatment. It was noted that ivermectin tablet after initial clearance of infection (faecal egg count reduction 100%), could not prevent establishment of new patent natural infection for even a single day, while ivermectin pour-on and injection prevented the establishment of new infection for 7 and 14 days post treatment, respectively. Maximum protection period (duration for which mean faecal egg count of sheep reaches 500 eggs per gram of faeces or more) of 68 days was recorded in sheep treated with injectable ivermectin, followed by pour-on (60 days) and oral (53 days) preparations.

Variation in resistance to haemonchosis: selection of female sheep resistant to Haemonchus contortus.

Seventy female lambs (6-7 months old) which were exposed to natural infections of Haemonchus contortus were designated as responders or non-responders on the basis of 10 weekly cumulative faecal egg counts. Selected responder and non-responder lambs were treated with ivermectin, housed separately and 6 weeks post-housing, seven lambs from each group were given a trickle infection of Haemonchus contortus at 1000 L3 daily for 5 days per week up to 2 weeks and examined weekly for 10 weeks after first infection. Analysis of data revealed significantly lower mean faecal egg counts and non-significantly less weight loss in responder than non-responder lambs. Mean values of haemoglobin, packed cell volume, total serum protein and peripheral eosinophil counts were significantly higher in responders than non-responders. In contrast, serum pepsinogen concentration was significantly less in responders than in non-responders. At 10 weeks post-infection, there were fewer pathological lesions and significantly lower worm burdens in responders than in non-responders. These results demonstrate a distinct resistance in responders to Haemonchus contortus infection.

Comparison of the post-parturient rise in faecal egg counts of indigenous and cross-bred ewes.

The breed differences in post-parturient rise (PPR) in faecal egg counts in lambing ewes of different breeds naturally infected with Haemonchus contortus were compared. The ewes of Nali, 50% Nali x 50% Russian Merino/Corriedale and 37.5% Nali x 62.5% Russian Merino/Corriedale were treated with fenbendazole while ewes of the above three breeds as well as 25% Nali x 75% Russian Merino/Corriedale, were kept untreated. Observations from 3 weeks before lambing to 12 weeks post-lambing at weekly intervals revealed that in treated ewes, egg counts of Nali did not differ significantly with 50% Nali whereas 37.5% Nali had significantly higher egg counts than those of Nali and 50% Nali. In untreated ewes egg counts of 50% Nali were significantly higher than that of Nali on some occasions, while 25% Nali had significantly higher egg counts than the other three breeds. None of the ewes from the Nali breed showed signs of haemonchosis, whereas few lambing ewes of the three Nali crosses (50%, 37.5% and 25% Nali) showed signs of haemonchosis and one ewe of the latter breed died.

Multiple anthelmintic resistance in Haemonchus contortus on a sheep farm in India.

Multiple resistance to benzimidazoles (fenbendazole, albendazole and mebendazole) in a strain of Haemonchus contortus in sheep was detected on a farm where fenbendazole 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 fenbendazole-resistant strain were treated with the recommended doses of various anthelmintics. Compared to the control group, percentage reductions in faecal egg counts of sheep treated with fenbendazole, albendazole, mebendazole, levamisole and morantel varied between 56% and 81% and worm counts between 71% and 86%. The results indicate the presence of multiple anthelmintic resistance in this strain of H. contortus on this farm. Sheep treated with ivermectin and closantel showed 100% reductions in faecal egg and worm counts, suggesting high efficacy of these drugs against the population of H. contortus on this farm.

Prevalence of fenbendazole resistance in ovine nematodes in north west India.

A survey was undertaken between March and September 1992 to assess the prevalence of fenbendazole resistance in sheep nematodes in 32 traditionally managed rural flocks and 22 intensively managed flocks on 3 farms. Fenbendazole, a commonly used anthelmintic was used at the recommended dose of 5 mg/kg body weight. Efficacy was determined on the basis of percentage reduction in strongyle faecal egg counts (FECR%) and larval cultures before and between 7 and 10 days after treatment. None of the traditionally managed rural flocks showed resistance and all had greater than 99% reduction in faecal egg counts after treatment. Of the 22 intensively managed flocks, however, 15 had slight fenbendazole resistance (between 60 and 90% reduction in egg counts) and 4 had severe resistance (less than 60% reduction).

Establishment of camel isolates of Haemonchus longistipes and Trichostrongylus colubriformis in goats.

Two main nematode parasites, Haemonchus longistipes and Trichostrongylus colubriformis, have been reported to cause morbidity and mortality in camels. Although goats are usually reared with camels in the combined animal husbandry system prevailing in Northern India, these parasites have not been reported in goats. Therefore, it was planned to conduct an experimental cross-transmission study of H. longistipes and T. colubriformis isolated from camels and transferred to young goats. Twelve healthy kids (5-6 months) were divided into three groups of four each. Groups I and II were infected orally with third stage infective larvae of H. longistipes and T. colubriformis cultured in the laboratory from faecal isolates from camels, at the rate of 50,000 and 100,000 larvae, respectively; group III comprised uninfected healthy controls. Daily clinical and faecal examinations were made. Body weights and blood haematological indices were measured at weekly intervals. The infection became established in both infected groups, and the animals started passing ova 17 days postinfection. Egg counts varied from 275.00 +/- 248.74 to 6150 +/- 2830.63 eggs g-1. Animals were killed 28 days postinfection. On postmortem examination mature as well as immature worms were recovered from the abomasum and intestine with typical postmortem changes seen in both the groups. Clinical manifestations were weakness and loss of body weight but no diarrhoea. There was a marked fall in haemoglobin and packed cell volume, indicating anaemia in both infected groups.

Susceptibility of two crossbreeds of sheep to Haemonchus contortus.

Studies were conducted on 20 crossbred lambs of 4-5 months old. Ten lambs were Nali x Corriedale cross (Hisardale) and the other 10 were Nali x Lohi cross (Munjal). Seven lambs each of both crossbreeds were infected with 10,000 infective larvae of Haemonchus contortus. Three lambs of each crossbreed served as uninfected controls. Clinicopathological examinations were done before and after infection and all the lambs were necropsied 28 days post-infection. The body weight gain, haemoglobin and packed cell volume were significantly lower in Hisardale lambs and the peripheral eosinophil count was significantly higher in Munjal lambs. Significant hypoalbuminaemia and hypoglobulinaemia, a sharp increase in albumin: globulin ratio; significantly higher faecal egg counts; adult worm counts; abomasal pH, volume, congestion and oedema were observed in Hisardale lambs as compared to Munjal lambs. Clinical signs of haemonchosis were more severe in Hisardale lambs and two of them died. Munjal lambs therefore seem less susceptible than Hisardale lambs to H. contortus infection.

An outbreak of haemonchosis associated with anthelmintic resistance in sheep.

An outbreak of haemonchosis associated with anthelmintic resistance was recorded in a flock of 150 crossbred lambs. Closantel and ivermectin were 100% effective against Haemonchus contortus while fenbendazole and morantel reduced faecal egg counts by 87 and 29%, respectively. Levamisole showed an efficacy of 95%. At double the recommended dose (10 mg kg-1), fenbendazole had an efficacy of 99% against H. contortus infection. This appears to be the first report of an outbreak of haemonchosis associated with fenbendazole and morantel resistance in a strain of H. contortus in sheep.

Efficacy of closantel against fenbendazole and levamisole resistant Haemonchus contortus in small ruminants.

Sheep infected with a fenbendazole resistant strain of Haemonchus contortus and goats with a levamisole resistant strain of the same parasite were used to evaluate the anthelmintic efficacy of closantel. Closantel at the rate of 10 mg/kg body weight was 100% effective against the 2 resistant strains of the parasite as indicated by faecal egg count and worm reduction. The efficacy of fenbendazole in sheep and of levamisole in goats was 56.68 and 76.90%, respectively.

Epidemiology of ovine helminthiasis in Haryana, India.

Tracer lambs were used to study the pasture contamination with infective stages of helminth parasites during one annual cycle in a subtropical climate. Post-mortem worm counts indicated that low infections with Haemonchus contortus occurred throughout the year except in June. However, twenty five or more H. contortus per lamb were recorded in January, April, May and August. Trichostrongylus colubriformis infection was detected throughout the year and 150 or more worms per lamb were recorded during January to May and in August. Anoplocephalids were recorded from the lambs throughout the year but had no seasonal pattern. Low infections with Oesophagostomum columbianum and Trichuris ovis were observed. The faecal egg counts from the permanent flock with whom the tracer lambs were grazed revealed heavy to mild worm burdens throughout the year. Coproculture indicated that H. contortus predominated from the second fortnight of May to December except in the second fortnight of July. Infection with T. colubriformis was more severe from January to the first fortnight of May and in the second fortnight of July. Negligible infections with O. columbianum, Bunostomum trigonocephalum, Gaigeria pachyscelis and Dictyocaulus filaria were also observed. Biohythergraphs prepared for H. contortus and T. colubriformis showed differences between observed and expected results. It is suggested that for realistic biohythergraphs related parameters in addition to rainfall and temperature should also be considered.