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Biomedical subjects

J Zinsstag

Publications and source records attributed to J Zinsstag.

At least 37 records · Page 2Linked to original sources
PubMed2003

Host specificity of Haemonchus spp. for domestic ruminants in the savanna in northern Ivory Coast.

Three Haemonchus species (Haemonchus contortus, Haemonchus placei and Haemonchus similis) live in sympatry in the savanna of North Côte d'Ivoire. Four domestic ruminant hosts (zebu-cattle, taurine-cattle, sheep and goats) share the same pastures throughout the year. Our post-mortem data imply that a Haemonchus spp. circulation exists among the different hosts species in the savanna of North Côte d'Ivoire. Under field conditions, mixed congeneric infections were the rule except in sheep where mono-specific H. contortus infections were the most frequent. The associations H.contortus+H.placei and H.placei+H.similis were dominant in goats and in cattle, respectively. In the populations examined, triple infections occurred in 11.5% of zebu-cattle and 29% of the taurine-cattle. Considering the intensities of infections, H. contortus was the main Haemonchus species of sheep and goats whereas H. similis was very rare in these host species. About 10% of the worms recovered in goats belong to the H. placei species. In cattle, H. contortus was very rare. H. placei was the dominant species in zebu-cattle (58.7% of the identified worms) and in taurine-cattle (73.9%) nevertheless, the proportion of H. similis was higher in zebu-cattle (38.6%) than in taurine-cattle (21.3%). Only few hybrids between H. placei and H. similis were found. The importance of such Haemonchus spp. circulation is discussed.

Animals↗
PubMed2003

Vector-borne diseases in humans and animals: activities of the Swiss Tropical Institute and risks for Switzerland.

The recent outbreak of anaplasmosis in a Swiss cattle herd triggered a discussion of the risk of vector-borne diseases in animals and humans in relation to climate changes and other factors. This overview presents the Swiss Tropical Institute's (STI) activities on vector-borne diseases (malaria, trypanosomosis, and leishmaniosis in humans and tick-borne diseases in livestock), describes the possible risks for humans and animals in Switzerland, and discusses options for action in the domains of public health, livestock production and companion animals. Switzerland is increasingly confronted with vector-borne diseases in humans and animals, but this is mainly due to an increase in imported cases. The emergence of a disease in one sector (human or veterinary medicine) may predict future trends in the other. A stronger intersectoral collaboration between public health and veterinary institutions at the federal and cantonal level is needed.

Animal Husbandry↗
PubMed2002

Seasonal epidemiology of ticks and aspects of cowdriosis in N'Dama village cattle in the Central Guinea savannah of Côte d'Ivoire.

In the Central Guinea savannah of Côte d'Ivoire, cattle breeding started only approximately 30 years ago. The impact of parasitism on the overall health status and productivity of the trypanotolerant N'Dama cattle in this area is unknown. In close collaboration with national veterinary institutions and local farmers, we studied spectrum, burden and seasonal dynamics of ticks (including aspects of cowdriosis) on N'Dama village cattle. In a longitudinal study, three randomly selected cattle herds (traditional farming type) of one village were examined repeatedly for ticks. Spectrum, burden, seasonal epidemiology of ticks were assessed. In these traditional herds (which lack (ecto)parasite management), all animals were infested by ticks at monthly counts. Five different tick species were identified; the four genera in order of frequency were: Amblyomma (overall prevalence 96%), Boophilus (47%), Hyalomma (<1%) and Rhipicephalus (<1%). Amblyomma variegatum was the most-abundant tick on cattle in all seasons. Seroprevalence of Cowdria ruminantium was 31% (95% CI: 26, 36%). Most of the animals typically carried low tick burdens. N'Dama cattle seem well adapted to their environment and can resist the tick burdens under this traditional farming system.

Animals↗
PubMed2000

Heritability of gastrointestinal nematode faecal egg counts in West African village N'Dama cattle and its relation to age.

Offspring-dam regression was used to estimate the heritability of strongyle faecal egg counts (FEC) of traditionally raised West African N'Dama cattle in the Central River Division in The Gambia. Faecal samples were taken monthly from June-October 1992, and again from July-October 1993, including 179-463 dams and their calves sampled on each occasion. The only proven genetic relationship was the dam-offspring relationship. Gastrointestinal strongyle FEC was expressed as epg (eggs per gram faeces). Regression of offspring FEC on dam FEC, showed a heritability (h(2)) of 0.18 (95% Confidence Limits 0.10, 0.25). Heritabilities were higher at the beginning and end of the rainy season than during the months of the peak rainy season. This is in line with earlier suggestions that genetic control of faecal egg counts is most effective during periods of low parasite transmission. There was a significant (p<0.001) increase in heritability of 0.086+/-0.018 with each year of age of the corresponding offspring. In view of the virtual absence of national cattle breeding systems in West Africa, which are a precondition for exploitation of heritable traits in cattle, integrated control using improved management and strategic prophylaxis remain the methods of choice to control gastrointestinal nematodes in the given conditions.

Africa, Western↗
PubMed1998

Biannual anthelmintic treatments in village Djallonke sheep in The Gambia: effects on productivity and profitability.

An on-farm deworming trial was conducted between 1991 and 1995 on traditionally managed Djallonke sheep in The Gambia to assess the impact on productivity and profitability of prophylactic biannual anthelmintic treatments- Fifteen private flocks with an average of 25 animals per flock participated in the experiment. Half of each flock was dewormed twice a year while the other half served as the control group. The two productivity traits that were significantly improved by the treatment scheme tested were the number of lambs per lambing which increased from 1.11 +/- 0.31 (Mean +/- S.D.) to 1.19 +/- 0.39 and the number of lambings per year which improved from 1.04 +/- 0.53 to 1.22 +/- 0.47. The mortality and weight at 12 months were not significantly affected by the treatment. Monitoring of sheep sales in the flocks and on surrounding markets allowed the calculation of a rate of return to the treatment scheme tested of 246%. Despite large variations in returns. The scheme studied is recommended as over 90% of the adopting farmers would yield positive returns to their investment.

Animal Husbandry↗
PubMed1998

Multiparasitism, Production and Economics in Domestic Animals in sub-Saharan West Africa.

Over the past ten years, an informal West African animal helminthosis network has developed (), with the aims of both improving livestock productivity through parasite control and, ultimately, increasing rural income. The network places a strong emphasis on building up local research capacity through scientific partnership. This article highlights recent findings from projects of the network.

Journal Article↗
PubMed1998

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Journal Article↗
PubMed1998

[Swiss veterinary research and development project in the Gambia: the point of view of the breeder concerning control of helminthiasis in livestock].

The epidemiology of nematodes in livestock in The Gambia was assessed. A prophylactic biannual treatment was then tested on cattle and sheep. This treatment resulted in a significant improvement in the reproductive performances (sheep: lambings/year increasing from 1.04 to 1.22 and lambs/lambing increasing from 1.11 to 1.19; cattle: age at first calving decreasing from 58 to 50 months) and, in cattle, a significant improvement of the weight (varying between 8% and 17% in 1 to 4 year old animals). A socioeconomic study conducted in parallel showed that the treatment in cattle is on average profitable (benefit/cost ratio of 1.14) but remains a risky investment which should not be generalised (benefit/cost ratio would have been below 1 in more than half of the participating herds). In sheep, the benefit/cost ratio is high (2.47) with a low risk of losses (< 10%). The obstacles to the adoption by farmers of such a treatment and the usefulness of a pluridisciplinary approach in similar studies are then discussed.

Animals↗
PubMed1997

Effect of strategic gastrointestinal nematode control on fertility and mortality of N'Dama cattle in The Gambia.

A large-scale longitudinal study was undertaken to investigate the effects of a strategic treatment of gastrointestinal nematodes on the mortality and fertility of N'Dama cattle under village conditions. Initially, 1046 animals from 26 private N'Dama cattle herds, were monitored from October 1989 to December 1994. Each herd was stratified by age and the animals were randomly allocated to two groups with a similar average age. One group received a single anthelmintic treatment of fenbendazole (Panacur, 7.5 mg/kg BW, Hoechst Veterinä AG) in October 1989, whereas the other group remained untreated. In July 1990, the herds were subdivided into two different treatment schemes. In the herds of scheme 1, the treated animals (Treatment group I) were treated once (in August), whereas in the herds of scheme 2, the treated animals (Treatment group II) were treated twice (in July and September). The same treatment schedule was used in the subsequent rainy seasons until December 1994. One group in every herd of both schemes served as control (Treatment group 0) and received no anthelmintic treatment throughout the study. The average annual cumulative incidence mortality between 0-1 year was more than two times higher in treated animals compared to their controls (21% against 7.5%). No differences were found in older age categories. Survival analysis confirmed differences in mortality from 0-1 year, but were not significant in proportional hazard models. The 25% quantiles of age at first calving was used to quantify differences between twice treated animals (50.2 months) and its controls (58.3 months) which represents a decrease of 8 months in twice treated animals. Annual calving rates of twice treated animals were 52.2% compared to 43.6% in the control group (P < 0.001), which is an increase of 8.6% to the control rate. Possible causes of increased mortality in 0-1 year old treated calves are discussed. We can conclude that in the present epidemiological situation and the given parasite spectrum, gastro-intestinal nematodes mainly affect host fertility. Strategic control of gastro-intestinal nematodes is thus recommended for young heifers up to their age of first calving provided the overall financial analysis of the intervention is beneficial.

Abortion, Veterinary↗
PubMed1997

Returns from strategic anthelmintic treatments in village cattle in the Gambia.

A large-scale study was undertaken to investigate the effects of two systematic anthelmintic treatments on village cattle productivity in the Gambia. Treated animals had significantly higher performance in terms of live weights and age at first calving, but the mortality rate of 0- to 1-yr-old cattle appeared to be negatively affected. These results and financial data on treatment costs were used in a herd simulation model to assess the profitability of the intervention. Treatment was profitable on average, but the risks of losing money were large and average returns were sensitive to various hypotheses examined. The treatment regimen studied can only be recommended in certain herds and further research is needed to identify the factors determining the negative response in other herds.

Aging↗
PubMed1997

Effect of strategic gastrointestinal nematode control on growth of N'Dama cattle in Gambia.

From October 1989 to December 1994, a longitudinal study on the control of gastrointestinal nematodes was done on 1000 N'Dama cattle in 20 private herds in Gambia. Each herd was divided into two groups with an even distribution of age and sex. One group received a single anthelmintic treatment of Fenbendazole, Panacur Hoechst Veterinär GmbH, 7.5 mg kg-1 BW in October 1989, whereas the other group served as an untreated control. In July 1990, the herds were subdivided into two different treatment schemes. In the herds of the first scheme the treated animals (Treatment group I) were treated once (in August), whereas in the herds of the second scheme the treated animals (Treatment group II) were treated twice (in July and September). The same treatment schedule was used in the subsequent rainy seasons until December 1994. One group in every herd served as control (Treatment group 0) and received no anthelmintic treatment throughout the study. One annual fenbendazole treatment had no significant effect on liveweights, whereas two annual treatments significantly increased liveweights of the age group 12-24 and 24-36 months by 9.4%, and 17.5%, respectively. Animals less than 12 months old had 6.3% higher liveweights after two treatments, the difference was statistically not significant (P < 0.06). Average weights of 3- and 4-year-old, twice-treated animals were 13.1% and 8.2%, respectively, higher compared with their controls. No effect of anthelminthic treatment on liveweights was found in 5-year-old and older animals. Herd structure analysis demonstrated that overall male offtake rates ranged from 12 to 28% in the 3-, 4- and 5-year-old age categories. The age categories within which deworming improves liveweights thus coincides with the age at which males are mainly sold. These results suggest that biannual metaphylactic treatments (end of July and beginning of September) of all animals from birth to an age of 4 years should be recommended, provided that the financial analysis demonstrates the profitability of this intervention.

Animals↗
PubMed1995

Effect of a single dry season anthelmintic treatment of N'Dama cattle on communal pastures in The Gambia.

The effect of a single anthelmintic treatment of cattle during the early dry season was studied. One hundred and sixty-six N'Dama cattle, 1-3 years old, were selected from five herds. There were 65 males and 101 females divided into two groups of 83 animals each. One group was treated with fenbendazole at 7.5 mg/kg body weight by mouth in November 1992; the other group remained as the untreated control. At monthly intervals from November 1992 to April 1993, each animal was weighed and the number of eggs/g of faeces (epg) was determined. The infective larvae (L3) were examined following culture of pooled samples from each group of animals. In April 1993, 6 animals (3 treated and 3 controls) from the herds under study were necropsied. The difference in the weight gains (4.6 kg) of the two groups was highly significant (p < 0.0001). The difference in the weight gains and the epg between the treated and control groups was influenced by the age of the animals. Of the treated animals, one contained no nematodes, one contained only 25 Oesophagostomum radiatum, and the third contained 25 Cooperia L4. The three untreated animals were all infected. It was concluded that the treatment in early dry season, with an anthelmintic effective against both adults and larvae, led to a significant reduction in egg counts, to elimination of adults and hypobiotic larvae and, consequently, to an increase in the body weight gain by the treated animals.

Animals↗
PubMed1995

Helminth parasites and hypobiosis of nematodes in N'Dama cattle during the dry season in The Gambia.

Three series of necropsies of cattle were performed, corresponding to early dry season, approximately 1 month after the last rains (November, n = 6), mid dry season (February, n = 6) and end dry season (April, n = 3). Eggs per gram of faeces (epg) were determined just before necropsy. Three trematodes (Fasciola gigantica, Schistosoma spp. and Paramphistomatids) and 11 nematodes were identified from cattle, with the prevalence rate varying from 6.7% to 100%. Haemonchus contortus was the most abundant nematode species, constituting from 81% (February) to 34.8% (April) of the total nematode burden. The proportion of L4 (indicating hypobiosis) of H. contortus was 85-99%. During the dry season, 44-67% of Oesophagostomum radiatum and 8-34% of Cooperia spp. population occurred as L4. There was no correlation between the number of worms found at necropsy and the epg. H. contortus survives almost exclusively as larvae in the abomasal mucosae, whereas Cooperia spp. and O. radiatum survive partly as larvae in the lumen, and also in nodules in the case of O. radiatum, and partly as hypometabolic adults with highly reduced fecundity. Trichostrongylus axei, T. colubriformis, Bunostomum phlebotomum, Strongyloides papillosus, Nematodirus spp. and Setaria labiatopapillosa occurred in small numbers.

Animals↗
PubMed1995

[Epidemiology of gastrointestinal helminthiasis in small ruminants in the tree-cropping pasture zone in Senegal].

An epidemiological survey on gastrointestinal helminthiasis in 51 sheep and 51 goats was held in the tree-cropping pasture region in Senegal from October 1990 to September 1991. All the animals examined were infected with at least 1 helminth species. Three trematodes (Fasciola gigantica, Schistosoma bovis, Amphistomatids), 2 cestodes (Moniezia expansa, Cysticercus tenuicollis) and 9 nematodes were identified. The most important parasite in sheep was Haemonchus contortus while Trichostrongylus colubriformis predominated in goats. The worm burden in sheep was significantly higher than in goats (P < 0.001). L4 larvae of H contortus were found in 85-87% of the small ruminants. There was a negative correlation between haematocrit, number of worms and egg per gram of faeces during the rainy season. These results show that the gastrointestinal nematode burden is high during the rainy season. During the dry season (9 months) nutritional problems are aggravated by adult worms and residual larvae.

Animals↗
PubMed1995

[Epidemiology of gastrointestinal nematodes in small ruminants in the plateau areas in Togo].

Post-mortem helminthological examinations were performed in Togo on small ruminants of the Djallonké breed (59 sheep, 60 goats), revealing the presence of eight gastrointestinal nematode species which were, in decreasing prevalence order, Trichostrongylus sp. (T. axei and T. colubriformis) (99%), Haemonchus contortus (82%), Strongyloides papillosus (67%), Cooperia curticei (43%), Oesophagostomum columbianum (40%), Gaigeria pachyscelis (36%) and Trichuris ovis (4%). The average worm burden was 1,367 +/- 146 in sheep and 1,133 +/- 102 in goats with an adult worm population peak in August-September (sheep: 2,135 +/- 494, goats: 2,066 +/- 270). During the dry season, Haemonchus contortus and Oesophagostomum columbianum populations were mainly in larval hypobiosis (L4). The number of eggs per gram faeces was usually high (> 3,000) and neither the species nor the age of the host (6 months to 3 years) played a significant role in helminth abundance.

Animals↗