Seasonal Prevalence of Gastrointestinal] nematodes of goats in Pernambuco state, Brazil

During each of 36 1-month periods from April 1979 to March 1982, 3–4 goats selected from typical farms were necropsied and examined for gastrointestinal nematodes. The goats were male, 12 months old, born on the farm and raised without any anthelmintic application. At the beginning of each month, from April 1981 to March 1982, three 12-month-old male goats shown to be free of gastrointestinal nematodes after anthelmintic treatment were grazedwith a flock of naturally infected goats (tracer goats). At the end of each month, these goats were placed on a cementfloored pen and were maintained there for 4 weeks prior to necropsy and examination for gastrointestinal nem nematodes.

Every goat examined was found to be parasitized by more than one species of nematode. Haemonchus contortus, Strongyloides papillosus and Oesophagostomum columbianum were the most prevalent nematodes found. Total worm burdens present in the farm animals were highest during late rainy/early dry season (March-June) and lowest in mid-rainy season (January-February). The acquisition of nematodes by tracer goats occurred mainly from mid-rainy to early dry season (January-June).     

Impact on beef cattle productivity of infection with anthelmintic-resistant nematodes

ABSTRACT

Aims: The main goal of the current study was to evaluate, on a commercial beef cattle farm, the impact of infection with gastrointestinal nematodes resistant to both ivermectin (IVM) and moxidectin (MXD) on the productivity of calves.

Methods: Male Aberdeen Angus calves, aged 9–11 months, with faecal nematode egg counts (FEC) ≥200 epg and body weight ≥190?kg, were allocated to two herds. Herd A (n?=?90) grazed a maize-winter forage crop rotation and Herd B (n?=?90) grazed a 2-year-old Agropyrum pasture. On Day 0 in each herd, calves were randomly allocated into five groups (n?=?18), which were treated with 0.2?mg/kg IVM; 0.2?mg/kg MXD; 3.75?mg/kg ricobendazole (RBZ), both IVM and RBZ, or remained untreated. Faecal samples collected on Days ?1 and 19 were used to determine the percentage reduction in FEC, and genera of the nematodes were determined by the identification of the third-stage larvae recovered from faecal cultures. Total weight gain was determined from body weights recorded on Days ?1 and 91.

Results: Overall mean reduction in FEC was 42% for IVM, 67% for MXD, 97% for RBZ and 99% for IVM?+?RBZ. The reduction in FEC for Cooperia spp. was ≤78% for IVM and MXD, and for Haemonchus spp. was 0 and 36% for IVM and MXD, respectively, confirming the presence of parasites resistant to both anthelmintics. Only IVM?+?RBZ treatment resulted in 100% efficacy against Haemonchus spp. The overall estimated mean total weight gain for calves treated with IVM was 15.7 (95% CI?=?11.9–19.7) kg and for calves treated with IVM?+?RBZ was 28.8 (95% CI?=?25–32.5) kg (p?<?0.001). Mean total weight gain for calves treated with MXD was 23.5 (95% CI?=?19.7–27.2) kg.

Conclusions and clinical relevance: In calves naturally infected with resistant nematodes, under the production system assessed here, weight gains were lower in calves treated with anthelmintics that were moderately or highly ineffective compared to those treated with highly effective anthelmintics. These results demonstrate to farmers and veterinarians the importance of a sustainable and effective nematode control under field conditions.     

The occurrence of anthelmintic-resistant sheep nematodes in the southern North Island of New Zealand

An analysis of veterinary diagnostic cases submitted to the Batchelar Animal Health Laboratory for faecal egg count reduction testing in sheep between 1986 and 1992 showed that 63% of them originated from properties carrying anthelmintic-resistant worms. Most of these cases involved resistance to a single drench type only, with the benzimidazoles being implicated most frequently. Overall, the figures suggested a frequency of occurrence of resistance to benzimidazole anthelmintics of 74%, to levamisole-type anthelmintics of 23% and to benzimidazo-lelevamisole combinations of 30%. No cases of resistance to milbemycin/avermectin-type drenches were recorded.     

Oxfendazole--anthelmintic activity in Egyptian goats artificially infected with gastrointestinal nematodes.

The recently developed benzimidazole anthelmintic, oxfendazole, was tested against artificial nematode infestations in Egyptian goats using oral dosing at 4.5 and 2.8 mg/kg. A 100% clearance of mature and immature Haemonchus contortus, Trichostrongylus axei, Ostertagia circumcincta, Coopera curticei, Bunostomum trigonocephalum and Chabertia ovina was obtained at the 4.5 mg/kg level. Very high levels of clearance against the mature worms were obtained at 2.8 mg/kg but the drug was less effective against immature worms at the lower dose rate. PCV, hemoglobin concentration and total erythrocyte counts declined after infection but became significantly (P less than 0.001) raised in treated animal.     

Misconceptions regarding the use of post-treatment larval cultures for the identification of anthelmintic-resistant sheep nematodes

Extract

In a recent communication⁽¹⁾, it was suggested that, without a corresponding measure of their initial abundance also, the results of post-treatment larval cultures undertaken to determine the identities of those nematode genera surviving an- thelmintic treatment during faecal egg count reduction (FECR) testing in sheep were likely to be largely meaningless. Since then, the validity of this statement has been queried by a number of veterinary practitioners who appear to assume that, in cases of anthelmintic resistance, the only nematode genera that might be expected to be represented in post-treatment larval cultures are those that are drench-resistant. That this latter assumption is unfounded, however, may be illustrated by an analysis of post-treatment larval culture results obtained from 102 ovine anthelmintic resistance cases identified by FECR testing at the Batchelar Animal Health Laboratory.     

An evaluation of an oral formulation of moxidectin against selected anthelmintic-resistant and -susceptible strains of nematodes in lambs

The efficacy of an oral formulation of the newly developed parasiticide, moxidectin, was tested against benzimidazole-resistant Haemonchus contortus, Trichostrongylus colubriformis, and Nematodirus spathiger, levamisole-resistant Ostertagia circumcincta, and susceptible Cooperia curticei infections in weaned lambs. Thirty-two lambs were experimentally infected with mixed doses of the above strains of nematodes. They were allocated into four treatment groups by stratified randomisation using liveweights and faecal egg counts 28 days later. One group received moxidectin at 0.2 mg/kg liveweight, one group oxfendazole at 4.5 mg/kg liveweight, one group levamisole at 7.5 mg/kg liveweight and the last group remained untreated as the control. Worm burdens in the lambs at slaughter 10 days after oral treatment confirmed the resistance status of the nematode strains used, and showed that moxidectin had a greater than 99.9% efficacy (p<0.01) against all of them. No adverse effects due to treatment with moxidectin were observed in any of the animals.     

Dietary copper sulfate for control of gastrointestinal nematodes in goats

Prevalence of anthelmintic resistance in gastrointestinal nematodes (GIN) of goats has necessitated studies for alternative means of control. The objective was to determine the effectiveness of dietary copper sulfate for control of GIN in meat goats. Naturally infected buck kids received 0 (LC), 78 (MC) or 158 (HC) mg copper sulfate (CS)/kid daily mixed with concentrate supplement for 63 days. After 42 days the HC group was re-randomized into either the LC or MC treatment. In another study, naturally infected yearling does were offered trace mineral mix with and without CS and intake was estimated to be 140-200mg CS/day. Goats grazed bermudagrass pastures and were rotated among two or three pastures to minimize pasture effects. Fecal egg count (FEC) and packed cell volume (PCV) were determined every 7 days in the first experiment and 14 days in the second experiment, and goats were weighed every 28 days. On Days 49 and 56 FEC were lower in the HC-treated kids (copper by day, P<0.02), but FEC were similar on all other days in the first experiment and were similar between the two groups of does in the second experiment. Blood packed cell volume was similar among treatment groups throughout both studies. Body weight was greater in LC compared with MC or HC-supplemented kids on Days 42 and 63 (copper by day, P<0.04). Body weights of does were similar on Days 0 and 56, but were reduced in those consuming trace mineral with CS on Day 28 (copper by day, P<0.03). Dietary CS failed to control GIN in this study.     

The efficacy of albendazole against some gastrointestinal nematodes in goats

On the basis of worm counts in naturally infected Angora-X goats, albendazole at either 3.8 mg/kg repeated after 24 hours or as a single dose at 7.6 mg/kg, was >99% effective in removing adult Ostertagia and Trichostrongylus spp. Small numbers of adult Haemonchus contortus, Cooperia sp. and Chabertia ovina were present in control but not treated animals. The single dose of 7.6 mg/kg removed >99% of adult Oesophagostomum venulosum whereas the repeated dose of 3.8 mg/kg removed only 96%.     

Prevalence of Sarcocystis species in sheep and goats in northern Nigeria.

Tissue samples comprising the oesophagus and diaphragm were collected from 400 sheep and 400 goats slaughtered at the abattoirs in the study area. Out of this number, 36 were positive for Sarcocystis cysts (sarcocysts) in sheep and 56 in goats. The sarcocysts in sheep measured 35.7 to 500 microns lengthwise and the cyst-wall 2.4 microns. They were identified to be Sarcocystis tenella. The cysts in goats measured 98 to 700 microns and the cyst-wall 2.7 microns. They were identified to be Sarcocystis capracanis. In both animals species, the sarcocysts were more frequent in the oesophagus than in the diaphragm. All sarcocysts seen were microscopic.