Biomedical subjects

J Vercruysse

Publications and source records attributed to J Vercruysse.

At least 19 recordsLinked to original sources

PubMed2006

Perinatal priming of calves born to Schistosoma mattheei-infected dams.

The objective of this study was to elucidate whether calves born to infected dams had been primed against Schistosoma mattheei antigens. Infection-confirmed, pregnant cows were randomly selected for monitoring their offspring. Pre-colostral serum was collected from the neonates for the detection of specific antibodies at birth, as they indicate a transplacental transfer of schistosome-specific antibodies and antigen. At the age of approximately 2 months, peripheral blood mononuclear cells (PBMC) of calves were analysed for specific memory by antigen-specific stimulation in vitro. Twenty-six of the 30 calves demonstrated S. mattheei-specific proliferation. All 12 seropositive-born, as well as 14 of the 18 seronegative-born (before colostrum uptake) calves displayed mattheei-specific proliferation. The results indicate that the calves were primed against S. mattheei and might explain why seropositive-born calves from infected dams are better protected against S. mattheei, and query the impermeability of the damaged ruminant placenta with consequences for antigen transfer.

Animals↗

PubMed2006

Epidemiological studies on Theileriosis and the dynamics of Theileria parva infections in Rwanda.

An epidemiological analysis based on three country wide surveys was carried out to determine the prevalence of infections with Theileria spp. in Rwanda. In the 1998 dry season, a total of 264 blood samples were submitted to Theileria spp. characterisation using the 18S species-specific PCR-RFLP assay. The same samples together with 634 samples (317 samples/season) collected during the 2002 dry season and the 2003 wet season were further analysed using the p104 Theileria parva specific PCR. The results from the 18S characterisation showed the presence of four Theileria spp., namely T. parva, T. mutans, T. taurotragi and T. velifera in the field. Half of the animals had multiple Theileria spp. infections. T. parva was the most prevalent and a high correlation (94%) was found between the prevalence results using the 18S and the p104 PCR assays. The prevalence of T. parva infections was stable over time and over season but decreased significantly from the high land to the low land areas. This unexpected trend cannot be explained alone by ecology or the dynamics of the tick population in the different zones, many other components such as breed type, tick control practices and grazing system are likely to play a role. Another important finding was the fact that young animals are infected early in life in all regions except in the high land zone indicating the existence of a particular epidemiological situation in this part of the country.

Animals↗

PubMed2006

Efficacy and specificity of RNA interference in larval life-stages of Ostertagia ostertagi.

RNA interference (RNAi) on parasitic nematodes has been described as successful and useful for the identification of novel drug and vaccine candidates. In this study we have evaluated this technology on the cattle parasite Ostertagia ostertagi. Eight different genes were targeted in L1 and L3 O. ostertagi larvae, by electroporation and soaking in dsRNA respectively. Down-regulation of target transcript levels was evaluated by semi-quantitative reverse transcriptase (RT) PCR. In L3 larvae, variable decreases in mRNA levels were observed for 5 genes, ranging from a complete knock down (tropomyosin, beta-tubulin) to a minor decrease (ATPsynthase, superoxide dismutase, polyprotein allergen). However, repeated experiments indicated that effects were sometimes difficult to reproduce. RNAi for ubiquitin, a transthyretin-like protein and a 17 kDa excretion secretion (ES) protein never resulted in a knock down of the transcript. The mRNA levels of 7 non-target genes showed no difference between larvae soaked in C. elegans control dsRNA versus O. ostertagi tropomyosin dsRNA, supporting that the observed reductions are specific for the target gene. Electroporation of L1 larvae proved to be less effective. Reductions in mRNA levels were only noticed for 2 genes and were not reproducible. In conclusion, the results indicate that the RNAi pathway is probably present in O. ostertagi but that the current RNAi techniques can not be used as a reliable screening method.

Animals↗

PubMed2006

Comparison of the transmissibility of Trypanosoma congolense strains, isolated in a trypanosomiasis endemic area of eastern Zambia, by Glossina morsitans morsitans.

Transmission experiments were conducted to compare the transmissibility of genetically different Trypanosoma congolense (Savannah subgroup) strains isolated from cattle in a trypanosomiasis endemic area of eastern Zambia. A total of 17 strains were compared. Three strains were extremely virulent with a short pre-patent period, high parasitaemia and a short median survival time (between 5 and 9 days) in mice. The remainder of the strains belonged to the moderate (6 strains) or low (8 strains) virulence categories with median survival times between 10 and 30 days and >30 days, respectively. Batches of 40 teneral Glossina morsitans morsitans (Diptera: Glossinidae) were offered a single bloodmeal on mice infected with one of those strains. Flies were dissected to determine their infection status 21 days later. The proportion of flies with procyclic and metacyclic infections differed significantly between trypanosome strains and were significantly higher in flies infected with extremely virulent strains (P=0.033 and P=0.016 for the differences in the procyclic infection rate of strains with moderate and low virulence, respectively and P=0.005 and P=0.019 for the differences in the metacyclic infection rate of strains with moderate and low virulence, respectively). On the other hand, moderately virulent strains had, in general, higher procyclic and metacyclic infection rates compared to low virulent strains. But the differences were not significant (P>0.05). The outcome of those experiments shows clear differences in transmissibility of trypanosome strains associated with their virulence. This observation confirms the theory for the evolution and maintenance of virulence in a parasite population and may explain the persistence of virulent trypanosome strains in a susceptible host population.

Animals↗

PubMed2006

Development and Bayesian evaluation of an ELISA to detect specific antibodies to Sarcoptes scabiei var suis in the meat juice of pigs.

Samples of ear scrapings, serum and diaphragmatic muscle were collected from 271 fattening pigs at the slaughterhouse. The scrapings were examined for the presence of mites, and tests for specific antibodies to Sarcoptes scabiei var suis in the serum and meat juice were made with an experimental ELISA. The cut-off value for the meat-juice ELISA was estimated at an optical density of 0.5 by receiver operating characteristic curve analysis, on the basis of the cut-off value for the serum ELISA of 0.4. The results of the three tests were used in a Bayesian model to estimate the characteristics of each test. The specificity of the tests of the ear scrapings was considered to be 1 and their sensitivity was estimated by Bayesian analysis to be 0.86, with a 95 per cent confidence interval (CI) of 0.73 to 0.99. The sensitivity of the meat juice ELISA (0.71, 95 per cent CI 0.6 to 0.8) and its specificity (0.77, 95 per cent CI 0.66 to 0.89) were comparable with the sensitivity (0.73, 95 per cent CI 0.6 to 0.8) and specificity (0.81, 95 per cent CI 0.69 to 0.95) of the serum ELISA.

Abattoirs↗

PubMed2006

Prevalence and genotyping of Cryptosporidium in three cattle husbandry systems in Zambia.

To estimate the prevalence of Cryptosporidium spp. in three different husbandry systems in Zambia, faecal samples were collected from calves up to the age of 3 months. Faecal consistency was scored for correlation with infection. Additionally, 45 positive samples were selected for genotyping by amplification of the 70-kDa heat shock protein (HSP-70) and the 18S rRNA gene. A total of 37 dairy, 25 beef and 92 traditional husbandry farms were visited: 250 samples were collected on dairy farms, 238 on beef farms and 256 on traditional husbandry farms. All samples were analysed using a commercial copro-antigen ELISA (Techlab)(Cryptospridium test). The calf prevalence in dairy, beef and traditional husbandry systems was 42.8%, 8.0% and 6.3%, respectively. Furthermore, 75.7% of the dairy farms, 44.0% of the beef farms and 15.2% of the traditional husbandry farms had at least one positive calf at the time of visit. Subsequently, there was a significantly higher Cryptosporidium parvum prevalence on dairy farms compared to beef or traditional farms (chi(2), P<0.001). On dairy farms low faecal consistency was correlated with C. parvum infection (chi(2), P<0.05). Both C. parvum and C. bovis were identified, although in one beef calf C. suis was found.

Age Factors↗

PubMed2006

Comparison of the virulence of Trypanosoma congolense strains isolated from cattle in a trypanosomiasis endemic area of eastern Zambia.

The virulence of 31 genetically different Trypanosoma congolense strains belonging to the Savannah subgroup and isolated from cattle at 11 sites in a trypanosomiasis endemic area of eastern Zambia was compared. Virulence testing, done in OF1 mice, revealed three virulence categories. Strains were considered extremely virulent when the median survival time ranged between 5 and 9 days. Moderately virulent strains had a median survival time between 10 and 30 days and low virulence, more than 30 days. For each strain, the prepatent period was determined and the PCV of the infected animals was measured at regular intervals. A total of six (19.4%) strains belonged to the extremely virulent category with a short prepatent period (mean 2.3+/-0.3 days), high parasitaemia, decline in PCV of 15.6+/-1.1% during the first 7 days p.i. and a short median survival time (mean 6 days). The remainder of the strains belonged to the moderate (13 strains) or low (12 strains) virulence categories with median survival times of 13 and 60 days, respectively. They had longer prepatent periods (means 3.2+/-1.6 days and 3.5+/-1.6 days for moderately virulent and strains with low virulence, respectively) and the decline in PCV was less steep (decline of 14.2+/-0.6 and 9.7+/-0.6% during the first 7 days of infection with moderately virulent strains and strains with low virulence, respectively). Extremely virulent strains were isolated from cattle at four sampling sites with 60% of the cattle from one sampling site harbouring such extremely virulent strains. Results from this study demonstrated substantial differences in the virulence of T. congolense strains of the Savannah subgroup, isolated in one geographic area from a single host species. On the assumption that information on virulence obtained from tests in mice can be extrapolated to cattle, the high proportion of strains with low to moderate virulence is thought to be attributed to the important role of susceptible cattle as reservoirs of trypanosomes in the study area and the ensuing selection against extremely virulent strains.

Animals↗

PubMed2006

The detection of anthelmintic resistance in nematodes of veterinary importance.

Before revised World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines on the detection of anthelmintic resistance can be produced, validation of modified and new methods is required in laboratories in different parts of the world. There is a great need for improved methods of detection of anthelmintic resistance particularly for the detection of macrocyclic lactone resistance and for the detection of resistant nematodes in cattle. Therefore, revised and new methods are provided here for the detection of anthelmintic resistance in nematodes of ruminants, horses and pigs as a basis for discussion and with the purpose that they are evaluated internationally to establish whether they could in the future be recommended by the WAAVP. The interpretation of the faecal egg count reduction test has been modified and suggestions given on its use with persistent anthelmintics and continuous release devices. An egg hatch test for benzimidazole (BZ) resistance is described. A microagar larval development test for the detection of benzimidazole and levamisole resistance provides third stage larvae for the identification of resistant worms. The sensitivity of these two tests can be increased by using discriminating doses rather than LD(50) values. Details are given of a PCR based test for the analysis of benzimidazole resistance in strongyles of sheep and goats, horses and cattle. Although promising for ruminant trichostrongyles, quantitative determination of gene frequency using real time PCR requires further development before PCR tests will be used in the field. Apart from faecal egg count reduction tests there are currently no satisfactory tests for macrocylic lactone resistance despite the great importance of this subject. Except for treatment and slaughter trials there are no validated tests for fasciolicide resistance or for the detection of resistance in cestodes.

Animals↗

PubMed2006

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of acaricides against (mange and itch) mites on ruminants.

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of the efficacy of acaricides against mange and itch mites on ruminants. Information is provided on the selection of animals, dose determination, dose confirmation and field studies, record keeping and result interpretation. These guidelines also are intended to assist the investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the worldwide adoption of standard procedures.

Animals↗

PubMed2006

Assessment of routine inspection methods for porcine cysticercosis in Zambian village pigs.

The value of tongue and meat inspection as diagnostic tools for porcine cysticercosis was assessed in 65 Zambian village pigs by comparing the results with carcass dissections. In addition, the intensity of infections, distribution and viability of cysts in infected pigs were measured. Five pigs (7.7%) were positive on tongue examination, while routine meat inspection showed 12 (18.5%) positives. However, carcass dissections detected cysticerci in 31 (47.7%) pigs. The range in number of cysticerci was 1 to 14,662 per carcass. Cysticerci were distributed throughout the carcass with the highest concentration in the heart, tongue and hind legs. In one animal 13 viable cysts were detected only in the brain. Fourteen pigs had more than 100 viable cysts, six between 2 and 100, and four had single cyst infections. Seven animals harboured only calcified cysts. These findings demonstrate the serious shortcomings of routine detection methods for porcine cysticercosis. While the specificity of tongue palpation and meat inspection was 100%, these tests failed to detect the infection in 83.9% and 61.3% of infected pigs, respectively.

Animals↗

PubMed2006

Taenia solium taeniasis and cysticercosis in three communities in north Vietnam.

OBJECTIVES: (1) To investigate the response to a serum antigen-detecting ELISA for cysticercosis and a stool coproantigen test for taeniasis in two rural communities (mountainous and coastal areas) and one group of (peri-)urban factory workers; and (2) to examine clinical features of human cysticercosis in northern Vietnam. METHODS: Villagers and factory workers and their families were informed and invited to participate in the study. Blood and faecal samples were collected from the participants and a simple questionnaire on taeniasis/cysticercosis completed. Serum was examined for the presence of circulating cysticercus antigen by a monoclonal-based sandwich ELISA. Ag-ELISA positive persons underwent a clinical examination and a computed tomography (CT) scan. Stool samples were examined microscopically for the presence of Taenia eggs and for copro-antigens. Tapeworms were identified following therapeutic expulsion using morphology and PCR-RFLP. RESULTS: Circulating cysticercus antigens, suggesting active infection, were detected in 5.3% (16/303), 0.6% (1/175) and 0.0% (0/229) of the sampled individuals from the mountainous, coastal and urban regions, respectively. Clinical examination and CT scan of the cysticercus antigen positive persons showed that active cysticercosis did not cause severe disease in most cases. Taenia copro-antigens were found in 0.3% (1/297), 1.8% (3/166) and 0.0% (0/228) of the stool samples from the mountainous, coastal and urban communities, respectively. Three tapeworms were expelled after treatment: two Taenia solium and one Taenia saginata. CONCLUSION: This survey points to a focal distribution of taeniasis/cysticercosis and suggests that human cysticercosis is rather acquired due to close contact with a T. solium carrier and self-infection, than through infection from the environment.

Adolescent↗

PubMed2006

Taeniasis-cysticercosis in Southern Ecuador: assessment of infection status using multiple laboratory diagnostic tools.

Taenia solium-taeniasis and cysticercosis were studied in the human and porcine populations of a rural community in the Southern Ecuadorian Andes. From the 1059 inhabitants, 800 serum samples and 958 stool samples could be collected. In addition, 646 from the estimated 1148 pigs were tongue inspected. Circulating antigen was detected by enzyme linked immunosorbent assay (Ag-ELISA) in 2.25% of the human population, whereas intestinal taeniasis was detected in 1.46% by the formalin-ether technique. Following treatment and recovery of tapeworm fragments these were all identified as T. solium. Porcine cysticercosis was diagnosed in 3.56% of the pigs by tongue inspection. In addition, enzyme linked immunoelectrotransfer blot (EITB) was performed on a subset group of 100 humans to confirm the results of the Ag-ELISA. One hundred serum samples from pigs were also analysed by EITB. It appeared that 43 and 74% of humans and pigs had antibodies against T. solium cysticerci, respectively. It is concluded that contrary to the high exposure of the human population to T. solium that is suggested by EITB, the number of active cysticercosis cases, diagnosed by Ag-ELISA, was low, which may indicate endemic stability. The further use of complementary diagnostic methods for a better understanding of the epidemiology of T. solium is suggested.

Adolescent↗

PubMed2005

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of acaricides against ticks (Ixodidae) on ruminants.

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of the efficacy of acaricides (excluding vaccines and other bio-control agents) against single and multi-host ticks (Ixodidae) on ruminants. Information is provided on the selection of animals, dose determination, dose confirmation and field studies, record keeping and result interpretation. The use of pen facilities is advocated for dose determination and confirmation studies for defining therapeutic and persistent efficacy. A minimum of two studies per tick species for which claims are sought is recommended for each dose determination and dose confirmation investigation. If dose confirmation studies demonstrate greater than 95% efficacy the sponsor may proceed to field studies, where a minimum of two studies per geographical location is preferred to confirm the therapeutic and persistent efficacy under field conditions. If dose confirmation studies demonstrate less than 95% efficacy then longer-term field studies can be conducted over two tick seasons with a minimum of two studies per geographical location. These studies can incorporate other control methods such as tick vaccines, to demonstrate stable long-term tick management. Specific advice is also given on conducting studies with paralysis ticks. These guidelines are also intended to assist investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new acaricides, and to facilitate the worldwide adoption of standard procedures.

Animals↗

PubMed2005

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against biting and nuisance flies on ruminants.

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of the efficacy of ectoparasiticides (excluding repellents) against the biting and nuisance dipteran flies of ruminants. Information is provided on the selection of animals, dose determination and dose confirmation studies, field studies, record keeping and result interpretation. These guidelines advocate the use of pen facilities for dose determination and dose confirmation studies. These guidelines also are intended to assist investigators on how to conduct specific studies, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the worldwide adoption of standard procedures.

Animals↗

PubMed2005

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against myiasis causing parasites on ruminants.

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of efficacy of ectoparasiticides against the myiasis causing parasites of ruminants. These guidelines specifically focus on larvicidal efficacy against myiasis causing flies. Information is provided on the selection of animals, dose determination and dose confirmation studies, field studies, record keeping and result interpretation. These guidelines advocate the use of pen facilities for dose determination and dose confirmation studies for defining therapeutic and persistent efficacy. These guidelines are also intended to assist investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the world-wide adoption of standard procedures.

Animals↗

PubMed2005

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against biting lice, sucking lice and sheep keds on ruminants.

These guidelines have been prepared to assist in the design, implementation and interpretation of studies for the assessment of the efficacy of ectoparasiticides against biting and sucking lice and sheep keds on ruminants. Information is provided on the selection of animals, dose determination, dose confirmation and field studies, record keeping and result interpretation. These guidelines advocate the use of pen facilities for dose determination and dose confirmation studies for defining therapeutic and persistent efficacy. These guidelines are also intended to assist investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision making process, to assist in the approval and registration of new ectoparasiticides, and to facilitate the world-wide adoption of standard procedures.

Animals↗

PubMed2005

[Protozoan infection causes diarrhea in calves].

The role of protozoan parasites in the etiology of diarrhea in calves is highlighted with emphasis on correct diagnosis. In neonatal calves, Cryptosporidium parvum is isolated in more than 44% of the faeces of diarrhetic calves. In calves older than one month, both Eimeria bovis and E. zuernii, and Giardia duodenalis are associated with diarrhea and poor growth. Clinical diagnosis has to be confirmed by examination of host faecal material. Both for C. parvum and G. duodenalis immunological assays are available. Control measures must aim to reduce or prevent oocyst or cyst transmission, by combining management measures, desinfection and chemotherapeutic treatment.

Animals↗

PubMed2005

Field evaluation of the efficacy of fenbendazole in captive wild ruminants.

The efficacy of in-feed fenbendazole at a dose rate of 7.5 mg/kg bodyweight for three consecutive days was assessed in five Arabian oryx (Oryx leucoryx), six scimitar-horned oryx (Oryx dammah), 14 slender-horned gazelles (Gazella leptoceros), eight Soay sheep (Ovis aries aries soay), 13 alpine ibex (Capra ibex ibex), six red deer (Cervus elaphus hippelaphus) and 11 Nelson's elk (Cervus elaphus nelsoni) kept in five herds in a zoo. The efficacy was assessed by means of repeated faecal egg count reduction (fecr) tests and in vitro egg hatch assays. Fenbendazole was highly effective against nematodes in five of the seven species, consistently reducing egg shedding by more than 90 per cent. In the egg hatch assays of the five herds, 50 per cent inhibition of hatching (ld50) was observed at a concentration of thiabendazole below 0.1 microg/ml. In the Arabian oryx and alpine ibex the efficacy of fenbendazole was less than 90 per cent, and the ld50 in the egg hatch assays was between 0.1 and 0.2 microg/ml thiabendazole.

Animals↗