Animals In Endemic Areas Research Articles

Foot and Mouth Disease Virus Strain-specific Antibody Titres in Naturally Infected or Vaccinated Bulls in Kenya

Foot-and-mouth disease (FMD) is a global viral infection that causes vesicular lesions in and around the mouth and feet, causing reluctance of animals to eat or move. In Kenya, bulls raised for AI receive vaccinations against FMD, but it is unclear if these animals experience vaccine-induced immunity. No research has been conducted to determine if animals in endemic areas develop natural immunity or whether animals in disease-free regions might be seropositive. This study aimed to determine the prevalence and levels of foot and mouth disease virus infection-triggered and vaccine-induced antibodies. A cross-sectional study was conducted on bulls farmed for AI production and vaccinated against FMD. Antibodies were quantified using a virus-neutralization test. One-way analysis of variance (ANOVA) and the Kruskal-Wallis test with Tukey and Dunn post-tests, respectively, were used to examine the data using the GraphPad InStat program. Additionally, the Spearman test was employed for correlation analysis and the t-test for intergroup differences analysis. A statistically significant P value was defined as less than 0.05. Findings showed protective antibody levels were present in 23%, 10.3%, 2.6%, and 7.7% of the animals in the FMD non-endemic region against the FMD virus strains O, A, SAT 1, and SAT 2, respectively. The protection provided by the O strain virus was significantly greater than that of SAT 1 (P = 0.01). In the FMD endemic area, all sampled animals showed protection levels at 100%, 100%, 100% and 29% for virus strains O, A, SAT 1, and SAT 2 respectively with the antibody titres showing significant differences (P < 0.05) for all the intergroup analysis except between strains O vs SAT 1 and A vs SAT 1 (P > 0.05). To conclude, the current research suggests that FMD may be making a comeback in the areas where the illness is not established. Furthermore, it seems that sperm recovery upon freezing is somewhat mitigated by FMDV-specific antibodies. The study advises monitoring FMD in areas where the illness is not endemic and confirms the current findings with larger sample sizes to enable more informed decision-making.

Seroprevalence and Risk Factors of Brucellosis in Abattoir Workers in Fars Province, Iran

Background & Objectives: Brucellosis remains an important occupational zoonotic disease, especially in developing countries. The disease is endemic in Iran and the Fars province. One of the main routes of brucellosis infection is at slaughterhouses, where the workers directly contact infected animals. This study was designed to estimate the seroprevalence of brucellosis among slaughterhouse workers in the Fars province, Iran. Materials & Methods: Ninety blood samples were collected from workers of two livestock slaughterhouses (Marvdasht and Kazeroon), in Fars, Iran. The sera were assessed for the Rose Bengal test (RBT), as a screening test for brucellosis, and the positive samples were subjected to the Wright test. The positive Wright samples were finally tested for the 2 -mercaptoethanol (2 -ME) agglutination test. Results: Brucellosis prevalence was 13.33% using RBT and 4.44% of the workers showed active brucellosis. No significant relationship was found between the questionnaire variables and brucellosis tests; exceptionally, there was a relationship between the workers' statements regarding having had brucellosis and RBT (P=0.01). Conclusion : Our study highlights the practical application of serological tests, including RBT, Wright, and 2 - ME as a simple strategy to monitor brucellosis and to diagnose and treat its active form in endemic regions. Although a small frequency of the disease was found, it could cause significant health and economic damage to humans and animals in endemic areas. Furthermore, taking enough protective measures is highly recommended for slaughterhouse workers to prevent human brucellosis.

Seroprevalence of severe fever with thrombocytopenia syndrome virus in medium-sized wild mammals in Miyazaki, Japan

Severe fever with thrombocytopenia syndrome (SFTS) is a fatal emerging tick-borne zoonotic disease caused by the SFTS virus (SFTSV). SFTSV infection in humans and companion animals is a matter of concern in endemic areas. Various wild animals are involved in the transmission cycle of SFTSV with vector ticks. Because the home range of medium-sized wild mammals commonly overlaps with humans’ living spheres, this study aimed to reveal the endemicity of SFTSV in such mammals. This study investigated the prevalence of antibodies against SFTSV and viral RNA in medium-sized wild mammals in Miyazaki Prefecture, Japan where human cases have been most frequently reported in Japan and performed a phylogenetic analysis to compare the detected SFTSV with those previously reported. Forty-three of 63 (68%) Japanese badgers (Meles anakuma) and 12 of 53 (23%) Japanese raccoon dogs (Nyctereutes procyonoides viverrinus) had antibodies against SFTSV. Japanese marten (n = 1), weasels (n = 4), and Japanese red fox (n = 1) were negative. Two of 63 (3%) badgers tested positive for SFTSV RNA, whereas the other species were negative. Phylogenetic analysis of the partial nucleotide sequence of SFTSV revealed that viral RNA detected from badgers exhibited 99.8% to 100% similarity to SFTSV, as previously reported in humans, cat, and ticks in the study area. This study demonstrated high seropositivity of antibodies in medium-sized wild mammals and suggested that SFTSV could be shared among these mammals, humans, and companion animals in endemic areas.

Comparative evaluation of Babesia bigemina truncated C-terminal rhoptry associated protein-1 and 200 kDa merozoite protein in indirect enzyme-linked immunosorbent assay

Babesia bigemina is an intra-erythrocytic apicomplexan protozoon which causes an acute as well as chronic disease in cattle and is transmitted by ixodid ticks throughout the world. Due to low sensitivity of microscopy for detection of the parasite, there is a need for developing effective diagnostic tests that can be used to identify carrier animals in endemic areas. In the present study, C-terminal fragment of rhoptry associated protein-1 (RAP-1/CT) and 200 kDa merozoite protein (P200/CT) of B. bigemina were cloned into pET-32a(+) expression vector and expressed in Escherichia coli as thioredoxin-fusion proteins for use in an indirect ELISA. The rRAP-1/CT and rP200/CT showed no cross reactivity with plasma from cattle infected with other common parasites namely Theileria annulata, Trypanosoma evansi, Cryptosporidium parvum and Anaplasma marginale in the standardized ELISA. Examination of 116 blood samples collected from cattle suspected for haemoprotozoan infections revealed that 17 (14.6%), 46 (39.6%), 52 (44.8%) and 53 (45.7%) were positive for B. bigemina by microscopy, nested PCR, rRAP-1/CT based and rP200/CT based indirect ELISA, respectively. The diagnostic sensitivities of rRAP-1/CT and rP200/CT indirect ELISAs were 97.8% and 91.3%, while the diagnostic specificities were 90% and 84.3%, respectively, when nested PCR was taken as a reference test. An almost perfect agreement (Kappa value -0.859) between rRAP-1/CT ELISA and nested PCR results, and a substantial agreement (Kappa value -0.737) between rP200/CT ELISA and nested PCR were noticed. The findings of the present study suggest that rRAP-1/CT is a better diagnostic candidate antigen than rP200/CT for diagnosis of B. bigemina infection and it may be used in an ELISA for surveillance or diagnosis of B. bigemina infection in bovines.

Leishmania infantum in wild animals in endemic areas of southern Italy

Leishmania infantum infection in wildlife is increasingly reported in Europe, but scant data are available in Italy so far. This study aimed to investigate the circulation of L. infantum among sylvatic hosts in Sicily (southern Italy), a highly endemic area for canine leishmaniosis, through serological and molecular tools. Target tissues (skin, spleen, lymph nodes) collected from 71 European rabbits, 2 European hares, 7 red foxes, 11 European wildcats and 1 pine marten, were qPCR analysed for the detection of L. infantum DNA. Additionally, 40 rabbits, older than one year, were serologically screened for specific anti-Leishmania antibodies. Leishmania infantum was molecularly diagnosed in 5.4% (n = 5) of the examined animals (3/71 European rabbits, 2/7 red foxes). In many of the qPCR positive animals (4/5), the parasite DNA was more prevalent in visceral than cutaneous tissues. None of the positive animal showed signs of disease and/or macroscopic alterations of organs; low parasitic burden in all positive tissue samples was also recorded. Only one rabbit serum (i.e., 2.5%) tested positive for anti-Leishmania antibodies. The seropositive rabbit was in good health status and no amastigotes were observed in lymph-node aspirate and blood smears.This study provides first evidence of L. infantum infection in wild animals from Sicily (southern Italy). Despite the low prevalence of infection here reported, the circulation of the Leishmania in wild reservoirs in Sicily remains worthy of future investigations for a better understanding of their role in the epidemiology of the disease as well as to fine-tune control strategies in the area.

Chemiluminescent ELISA with multi-epitope proteins to improve the diagnosis of canine visceral leishmaniasis

Diagnosing canine visceral leishmaniasis (CVL) is difficult because clinical signs of the disease are non-specific and a many infected animals in endemic areas, as in Brazil, are asymptomatic. Serological tests are the most common diagnostic methods employed, but most have limitations. For this reason, the implementation of a rapid, sensitive, and specific diagnostic test for CVL has become increasingly important. In this study, we adapted a chemiluminescent enzyme-linked immunosorbent assay (CL ELISA), using two multi-epitope recombinant proteins (PQ10 and PQ20) and a crude Leishmania antigen produced using promastigotes of L. infantum, as antigens to detect CVL infection in animals from Belo Horizonte. To investigate cross-reactions, samples from dogs with other infections (babesiosis, ehrlichiosis and Trypanosoma cruzi) were tested. Assay performance validations were conducted to analyse parameters such as variability, reproducibility, and stability.CL ELISA sensitivity/specificity with PQ10 antigen was 93.1%/80.0%; with the PQ20 protein 93.1%/96.6%; and with the crude antigen 75%/73.3%. Inter-assay variability and inter-operator coefficient of variation were <7% and <15%, with PQ10 and PQ20, respectively. The accuracy of the CL ELISA was classified as excellent for PQ10 (AUC = 0.95) and PQ20 (AUC = 0.98) and moderate for the crude antigen (AUC = 0.77). The kappa score for qualitative agreement between two plate lots was excellent for PQ10 (0.89) and good for PQ20 (0.65). PQ20 remained more stable than PQ10. The CL ELISA with recombinant proteins is a promising tool to diagnose CVL.

Fascioliasis

Fascioliasis is infection by liver flukes, Fasciola spp. The two species that infect humans are Fasciola hepatica and Fasciola gigantica. Other herbivorous animals such as cattle, goats, water buffalo, horses, camels, hogs, rabbits, and deer can be infected with Fasciola spp. Humans acquire Fasciola after ingestion of food and water that are contaminated with Fasciola metacercaria, especially aquatic plants. Fascioliasis is usually mild disease in human. Clinical manifestrations are related with the the phases of infection. In migratory phase, symptoms may occur when metacercariae excyst in the duodenum and young liver flukes migrate through the intestinal wall to the liver capsule and hepatic parenchyma before reaching the bile ducts. Clinical symptoms include abdominal pain in the right hypochondrium, dyspepsia and anorexia, nausea, vomiting, and hepatomegaly. Systemic manifestration such as urticaria and eosinophilia are also common presentation. After Fasciola reside in the biliary tract, most of cases are asymptomatic. Biliary track obstruction can accidentally occur and might lead to cholangitis. Triclabendazole 10 mg/kg as a single dose is the current drug of choice for fascioliasis treatment and triclabendazole two doses of 10 mg/kg for 1 day is effective in severe or persistent infections, with cure rates of 79% and 92%, respectively. Currently, there is no vaccine for prevent Fasciola infection. Proper cooking or cleaning food especially aquatic plants before consumption will prevent accidental Fasciola infection. Adequate mass treatment among infected animals in endemic areas and proper sanitary in the livestock farm are important for disease control.&#x0D; &#x0D; Figure 1 ภาพถ่ายตัวเต็มวัยพยาธิ Fasciola hepatica (Linnaeus, 1758) (A) และ Fasciola gigantica (Cobbold, 1855) (B)(ได้รับการอนุเคราะห์ภาพจาก รศ.ดร.อุรุษา แทนขำ ภาควิชาปรสิตหนอนพยาธิ คณะเวชศาสตร์เขตร้อน มหาวิทยาลัยมหิดล) &#x0D;

Unravelling the epidemiology of tick paralysis in Australia: Application of passive surveillance and GIS

Unravelling the epidemiology of tick paralysis in Australia: Application of passive surveillance and GIS

Seroepidemiology of CCHF in Domestic Animals in Endemic Areas in Albania

Abstract Crimean-Congo hemorrhagic fever (CCHF) is an arboviral zoonotic infection wich is endemic in some areas of the country. The aim of this study was to assess the seroprevalence of CCHFV in previous and recent endemic areas of the country. This crosssectional serologic study was conducted in period 2010-2014 by the Institute of Public health in Tirana, Albania. The survey included 152 sera specimen of cattle which were randomly collected from seven districts in Albania over the period 2010-2014. All samples were collected randomly from seven districts in Albania and were examined for anti-CCHFV IgG. Of the total of 152 samples examined, 102 (67.1%) were positive to IgG ELISA. The highest positivity rate was among cows (88.3%) and in recent endemic areas of Has and Kukes, 89.7% and 82.9% respectively. In recent endemic areas humans can potentially contract the disease as compared to other areas of the country.

Reservoir Animals and Their Roles in Transmission of Opisthorchis viverrini.

Although any fish-eating mammals could be potential definitive hosts of Opisthorchis viverrini, only a few, especially cats and dogs, are actually known reservoir hosts for this parasite. Both animals usually get infected via consuming raw or undercooked contaminated fish, fish dishes or food remains from households. The infected animals sustain parasite egg spread via open environment defecation. Cats are the most important reservoir with higher prevalence rates of O. viverrini infection than dogs in endemic areas. Usually Opisthorchis-infected animals do not exhibit apparent clinical symptoms or specific abnormalities in laboratory examinations. Pathological findings in these animal reservoirs are basically similar to those seen in humans and experimental animals, namely periductal inflammation, biliary hyperplasia and periductal fibrosis. However, O. viverrini-associated cholangiocarcinoma has not yet been reported in the reservoir animals at present. Praziquantel is a treatment of choice not only for humans but also for animal reservoirs. Integrated control of opisthorchiasis in animal reservoirs is based on holistic approaches such as EcoHealth/One Health concepts. In fact integrated control of opisthorchiasis in humans in ecosystem has also proved successful, for example, the Lawa model for opisthorchiasis control in the endemic area of Khon Kaen, Thailand. Other feral and wild animals in endemic areas might also be potential reservoirs, and this requires more investigation. In addition, genetic diversity and evolution of the flukes might also influence zoonotic capability.

Genetically modified rabies virus-vectored Ebola virus disease vaccines are safe and induce efficacious immune responses in mice and dogs

Ebola viruses (EBOVs) are zoonotic pathogens that cause EBOV disease (EVD) with high case fatality in humans. Currently, EVD vaccines are still under development in several countries. Here, we generated two recombinant rabies viruses (RABVs), rERAG333E/ZGP and rERAG333E/SGP, expressing the Zaire EBOV glycoprotein (ZGP) or Sudan EBOV glycoprotein (SGP) gene based on a modified ERA vaccine strain (rERAG333E) vector platform. The recombinant RABVs retained growth properties similar to those of the vector virus in BSR cell culture and efficiently expressed ZGP or SGP. After intracerebral (i.c.) inoculation with rERAG333E/ZGP or rERAG333E/SGP, all adult mice showed no signs of disease or weight loss and suckling mice maintained similar survivorship curve as those mice inoculated with control vector rERAG333E, demonstrating that ZGP or SGP expression did not increase the virulence of the vector. Mouse immunization studies showed that vaccination with rERAG333E/ZGP and rERAG333E/SGP induced Zaire or Sudan EBOV neutralizing antibody (VNA) responses and IgG, IgG2a responses to ZGP or SGP, suggesting their potential as oral or inactivated bivalent vaccines against rabies and EVD. Most importantly, all dogs immunized orally with rERAG333E/ZGP developed long-lasting ZEBOV and RABV VNA responses with or without previous rabies vaccine immunization history. Live rERAG333E with EBOV GP thus appear to have the potential to be oral vaccines for free-roaming animals in endemic areas of EVD and rabies, and may serve as inactivated vaccines for use in humans.

Burkholderia pseudomallei in soil samples from an oceanarium in Hong Kong detected using a sensitive PCR assay

Melioidosis, caused by Burkholderia pseudomallei, is an emerging infectious disease with an expanding geographical distribution. Although assessment of the environmental load of B. pseudomallei is important for risk assessment in humans or animals in endemic areas, traditional methods of bacterial culture for isolation have low sensitivities and are labor-intensive. Using a specific polymerase chain reaction (PCR) assay targeting a Tat domain protein in comparison with a bacterial culture method, we examined the prevalence of B. pseudomallei in soil samples from an oceanarium in Hong Kong where captive marine mammals and birds have contracted melioidosis. Among 1420 soil samples collected from various sites in the oceanarium over a 15-month period, B. pseudomallei was detected in nine (0.6%) soil samples using bacterial culture, whereas it was detected in 96 (6.8%) soil samples using the specific PCR assay confirmed by sequencing. The PCR-positive samples were detected during various months, with higher detection rates observed during summer months. Positive PCR detection was significantly correlated with ambient temperature (P<0.0001) and relative humidity (P=0.011) but not with daily rainfall (P=0.241) or a recent typhoon (P=0.787). PCR-positive samples were obtained from all sampling locations, with the highest detection rate in the valley. Our results suggest that B. pseudomallei is prevalent and endemic in the oceanarium. The present PCR assay is more sensitive than the bacterial culture method, and it may be used to help better assess the transmission of melioidosis and to design infection control measures for captive animals in this unique and understudied environment.

Prevalence and haemato-biochemical profile of Anaplasma marginale infection in dairy animals of Punjab (India)

ObjectiveTo do the systematic comparison of prevalence of anaplasmosis by PCR and Giemsa stained thin blood smear (GSTBS) based parasitological assays in dairy cattle of Punjab, which has not been reported yet. To analyse the haematobiochemical alterations in infected animals to arrive at the conclusion regarding the pathogenicity induced by Anaplasma marginale (A. marginale) in latent and patent infection. MethodsStudy was conducted on 320 animals (236 cows, 62 calves and 22 buffaloes) of Punjab, India. PCR on genome of A. marginale was performed by targeting msp1 β gene using specific primers BAP-2/AL34S, amplifies products of size 407 bp. Questionnaires based data on the characteristics of the infected animals and management strategies of the farm were collected and correlated. ResultsHigher prevalence and more significant association was observed in the PCR based molecular diagnosis (P=0.00012) as compared to that in GSTBS (P=0.028 8) based diagnosis with various regions under study. With respect to the regions, highest prevalence was recorded in Ferozepur by PCR based diagnosis, while that in Jalandhar by GSTBS examination. Similar marked significant association of the PCR based diagnosis with the age of the animals under study (P=0.00013) was observed elucidating no inverse age resistance to A. marginale in cow calves. Haematobiochemical profile of infected animals revealed marked anemia, liver dysfunction and increase globulin concentrate indicating rise in immunoglobulin level to counteract infection. ConclusionsPCR is far more sensitive in detecting the disease even in latent infection which may act as nidus for spread of anaplasmosis to susceptible animals in endemic areas. Severity of anaemia and liver dysfunction were comparable both in patent as well as latent infection indicating pathogenicity of both.

Complete Killing of Caenorhabditis elegans by Burkholderia pseudomallei Is Dependent on Prolonged Direct Association with the Viable Pathogen

Background Burkholderia pseudomallei is the causative agent of melioidosis, a disease of significant morbidity and mortality in both human and animals in endemic areas. Much remains to be known about the contributions of genotypic variations within the bacteria and the host, and environmental factors that lead to the manifestation of the clinical symptoms of melioidosis.Methodology/Principal FindingsIn this study, we showed that different isolates of B. pseudomallei have divergent ability to kill the soil nematode Caenorhabditis elegans. The rate of nematode killing was also dependent on growth media: B. pseudomallei grown on peptone-glucose media killed C. elegans more rapidly than bacteria grown on the nematode growth media. Filter and bacteria cell-free culture filtrate assays demonstrated that the extent of killing observed is significantly less than that observed in the direct killing assay. Additionally, we showed that B. pseudomallei does not persistently accumulate within the C. elegans gut as brief exposure to B. pseudomallei is not sufficient for C. elegans infection.Conclusions/SignificanceA combination of genetic and environmental factors affects virulence. In addition, we have also demonstrated that a Burkholderia-specific mechanism mediating the pathogenic effect in C. elegans requires proliferating B. pseudomallei to continuously produce toxins to mediate complete killing.

Clinical and Imaging Manifestations of Hemorrhagic Pulmonary Leptospirosis: A State-of-the-Art Review

Leptospirosis, a spirochetal zoonosis, is frequently unrecognized due to its manifestation as an undifferentiated fever. It is an emerging infectious disease that has changed from an occupational disease of veterinarians, farmers, butchers, and other animal handlers to a cause of epidemics in poor and decayed urban communities in developing countries. Humans are infected when mucous membranes or abraded skin come into direct contact with the urine of infected animals, especially rats and dogs. Mortality from severe leptospirosis is high, even when optimal treatment is provided. The diagnosis of leptospirosis is based on clinical findings, history of direct or indirect exposure to infected animals in endemic areas, and positive serological tests. It should be considered in the differential diagnosis of patients with febrile illnesses associated with pneumonitis and respiratory failure, especially when hemoptysis is present. Severe pulmonary involvement in leptospirosis consists primarily of hemorrhagic pneumonitis. In advanced cases, adult respiratory distress syndrome and massive pulmonary hemorrhage may occur. Chest radiographs show bilateral alveolar infiltrates and/or resemble viral pneumonia, bronchopneumonia, tuberculosis, adult respiratory distress syndrome, and other causes of pulmonary hemorrhage such as Goodpasture syndrome. High-resolution computed tomography scans may show nodular infiltrates, areas of consolidation, ground-glass attenuation, and crazy-paving patterns. Bronchoalveolar lavage and autopsy studies have suggested that ground-glass opacities and air-space consolidations are secondary to pulmonary hemorrhage. Although not specific, the presence of these computed tomography findings in a febrile patient with an appropriate history should suggest a diagnosis of leptospirosis.

Immunogenic Burkholderia pseudomallei outer membrane proteins as potential candidate vaccine targets.

Background Burkholderia pseudomallei is the causative agent of melioidosis, a disease of significant morbidity and mortality in both human and animals in endemic areas. There is no vaccine towards the bacterium available in the market, and the efficacy of many of the bacterium's surface and secreted proteins are currently being evaluated as vaccine candidates.Methodology/Principal FindingsWith the availability of the B. pseudomallei whole genome sequence, we undertook to identify genes encoding the known immunogenic outer membrane protein A (OmpA). Twelve OmpA domains were identified and ORFs containing these domains were fully annotated. Of the 12 ORFs, two of these OmpAs, Omp3 and Omp7, were successfully cloned, expressed as soluble protein and purified. Both proteins were recognised by antibodies in melioidosis patients' sera by Western blot analysis. Purified soluble fractions of Omp3 and Omp7 were assessed for their ability to protect BALB/c mice against B. pseudomallei infection. Mice were immunised with either Omp3 or Omp7, subsequently challenged with 1×106 colony forming units (cfu) of B. pseudomallei via the intraperitoneal route, and examined daily for 21 days post-challenge. This pilot study has demonstrated that whilst all control unimmunised mice died by day 9 post-challenge, two mice (out of 4) from both immunised groups survived beyond 21 days post-infection.Conclusions/SignificanceWe have demonstrated that B. pseudomallei OmpA proteins are immunogenic in mice as well as melioidosis patients and should be further assessed as potential vaccine candidates against B. pseudomallei infection.

The Sb14-3-3ζ recombinant protein protects against Schistosoma bovis in BALB/c mice

Schistosoma bovis is a trematode parasite mainly affecting cattle and sheep. Evidences about the arise of drug resistance and the high rates of re-infection of animals in endemic areas have pointed out the need of developing new control tools, e.g., effective vaccines. Schistosomes 14-3-3 proteins have been defined as vaccine candidates against respective infections. We have therefore investigated the protective capacity of the 14-3-3 protein from S. bovis – Sb14ζ – against S. bovis in mice. In addition, we have addressed the influence of the co-administration of four different immunomodulators with the 14-3-3 polypeptide. The values of protection against S. bovis were statistically significant when the Sb14ζ was combined in two independent experiments with the AA0029 (61.0% and 40.31%), AA2829 (49% and 36.3%) and PAL (49% and 40.075%) immunomodulatory molecules. Immune responses from vaccinated animals showed that the highest protection rates do not necessarily match with a dominant Th1-type response.

Serological diagnosis of visceral leishmaniasis by an enzyme immunoassay using protein A in naturally infected dogs

A rapid indirect enzyme-linked immunosorbent assay (ELISA) was developed for measuring antibodies against Leishmania chagasi using total antigen from lysed promastigotes. Fifty symptomatic mixed breed dogs from a region of high incidence of visceral leishmaniasis in Brazil were examined. The results showed that in the positive animals, diagnosed by cytological examination, the ELISA using protein A assay system (mean optical density ± SD / 2.078 ± 0.631) detected more antibodies than the anti-IgG assay (mean optical density ± SD / 1.008 ± 0.437), while in the negative animals, the results by both systems were similar. These results suggest that the ELISA assay using protein A peroxidase conjugated could be useful to detect early infected animals in endemic areas, and thus help to control the spread of the infection.

The Leucocytic and Parasitaemic Profiles and Immune Response of Rats Treated with Retinyl Palmitate before Infection with Trypanosoma brucei

The effects of oral administration of retinyl palmitate (30 000 IU/kg bodyweight) for 3 days to rats before infection with Trypanosoma brucei were investigated by examining the leucocytic and parasitaemic profiles, and the antibody response to sheep red blood cells. The pretreatment significantly ( P<0.01) improved the leucocytic profile (especially the absolute lymphocyte count) from day 7 post-infection to the time of death. It also significantly delayed the onset of parasitaemia (i.e., lengthened the pre-patent period) and led to reduced levels of parasitaemia throughout the period of infection. Pretreatment significantly increased the antibody response to sheep red blood cells ( P<0.01) throughout the infection, even after treatment with diminazene aceturate, to levels that more than compensated for the immunosuppressive effect of the T. brucei. Further studies are warranted on the possible use of retinyl palmitate in overcoming immunosuppression associated with trypanosome infections in man and animals in endemic areas.

Ecological factors rather than temporal factors dominate the evolution of vesicular stomatitis virus.

Vesicular stomatitis New Jersey virus (VSV-NJ) is a rhabdovirus that causes economically important disease in cattle and other domestic animals in endemic areas from southeastern United States to northern South America. Its negatively stranded RNA genome is capable of undergoing rapid evolution, which allows phylogenetic analysis and molecular epidemiology studies to be performed. Previous epidemiological studies in Costa Rica showed the existence of at least two distinct ecological zones of high VSV-NJ activity, one located in the highlands (premontane tropical moist forest) and the other in the lowlands (tropical dry forest). We wanted to test the hypothesis that the viruses circulating in these ecological zones were genetically distinct. For this purpose, we sequenced the hypervariable region of the phosphoprotein gene for 50 VSV-NJ isolates from these areas. Phylogenetic analysis showed that viruses from each ecological zone had distinct genotypes. These genotypes were maintained in each area for periods of up to 8 years. This evolutionary pattern of VSV-NJ suggests an adaptation to ecological factors that could exert selective pressure on the virus. As previous data indicated an absence of virus adaptation to factors related to the bovine host (including immunological pressure), it appears that VSV genetic divergence represents positive selection to adapt to specific vectors and/or reservoirs at each ecological zone.