Field evaluation of an exoantigen-containing Babesia vaccine in Venezuela

Bovine babesiosis is endemic in Venezuela, causing significant losses in highly susceptible imported cattle. Current immunoprphylatic methods include the less desirable use of live parasites. Inactivated vaccines derived from exoantigen-containing supernatant fluids of in vitro Babesia bovis and B. bigemina cultures have been developed and constitute a major improvement in vaccine safety, stability and ease of handling. Vaccination trials conducted under field conditions provide the final evaluation of a culture-derived B. bovis-B. bigemina vaccine. During a 5-year period, approximately 8,000 cattle were vaccinated and 16 clinical trials carried out in. 7 states of Venezuela Clinical, serologic and parasitologic data were collected monthly from 10% of the animals over a 2-year period. Data were also collected from a similar number of nonvaccinated control cattle. Analysis of results from these trials demonstrated a reduction in the incidence of clinical disease among vaccinated animals and complete protection against mortality among vaccinated and nonvaccinated cattle. Use of this inactivated vaccine offers the best combination od safety, potency and efficacy for thew immunoprophylatic control of bovine babesiosis.

Successful vaccination against Boophilus microplus and Babesia bovis using recombinat antigens

Current methods for the control of the cattle tick Boophils microplus and the agent of bovine babesiosis, Babesia bovis are unsatisfactory. Effective immunological control of both parasites would have great advantages. However, naturally acquired immunity to the tick is generally unable to prevent serious production losses. A vaccine against the tick, based on a novel form of immunization, is being developed. A protective antigen has been isolated from the tick, characterized and produced as an effective, recombinant protein. A vaccine incorporating this antigen is currently undergoing field trials. In the Australian situation, improved tick control will probably increase endemic instability with respect to B. bovis. Fortunately, a trivalent, recombinant B. bovis vaccine has also been developed. This too is now undergoing pre-registration field trials.

Subtelomeric structure of Plasmodium falciparum chromosomes

Previous studies of subtelomeric regions in Plasmodium berghei led to the identification of subtelomeric repeats (2.3kb long) present in a variable number at many chromosomal ends. Both loss and increase in 2.3kb-repeat copy number are involved in chromosome-size polymorphisms. Subtelomeric losses leading to chromosome-size polymorphisms have been described by several authors in P.falciparum where the structure of subtelomeric regions is not known in detail. We therefore undertook their characterisation, by means of chromosome walking and jumping techniques, starting from the telomere-flanking sequence present in pPftel.1, the P.falciparum telomeric clone described by Vernick and McCutchan (1988). The results indicate that at least 20 (out of 28) chromosomal ends in P.falciparum 3D7 chromosomes share a subtelomeric region, about 40kb long, covering (but not limited to) the Rep20 region. Non repetitive, AT-rich portions flanking the Rep20 region on both sides are also conserved at most chromosomal ends.

The biology of Aedes (Ochlerotatus) albifasciatus Macquart, 1838 (Diptera: Culicidae) in Central Argentina

Aedes albifasciatus is a flood water mosquito ocurring in the southern countries of South America. It is a competent vector of the Western Equine Encephalitis (WEE) and causes important losses on milk and beef production in central Argentina. Field work was carried out from December 1990 to March 1993, on a monthly basis during the dry season and biweekly during the rainy season. Larvae were collected using the 'dipping' technique and females with CDC traps baited with CO2. Field collected larvae were used to build laboratory cohorts, from which basic population parameters were estimated. Eggs survived up to six months on dry soil, although there was a linear decrease of viability with time. At 23ºC, larval development time was around nine days, and all adults emerged within one week. The estimation of larval development in the laboratory seems to be very near the development on the field, as larvae have been collected on average eight days after a rainfall. Egg to adult survival was 83%, with the highest mortality on fourth larval instar (6%). In the laboratory studies, sex proportion among the adults was 1:1, females lived longer than males (median 13 and five days, respectively), and adult survival pattern showed a constant number of individuals dying per unit time. Field collected females layed an average of 84 eggs per batch, and completing up to five gonotrophic cycles, suggesting an estimated survival of up to 35-50 days.

Neotropical monogenoidea. 25. Anacanthorus penilabiatus n. sp. (Dactylogyridae, Anacanthorinae) from Piaractus mesopotamicus (Osteichthyes, Serrasalmidae), cultivated in the State of São Paulo, Brazil

Anacanthorus penilabiatus n. sp. is described from the serrasalmid fish, Piaractus mesopotamicus (Holmberg, 1887), cultivated in the Centro de Aqüicultura, Universidade Estadual Paulista. The new species is characterized by having a relatively straight copulatory organ with a long "lip" on the distal margin and a median longitudinal flap, and a copulatory ligament. The large size of the infrapopulations of this species of parasite indicates that it should be considered a potential agent causing losses in aquaculture of the fish host.

Immune Response of Cattle Infected with African Trypanosomes

Trypanosomosis is the most economically important disease constraint to livestock productivity in sub-Saharan Africa and has significant negative impact in other parts of the world. Livestock are an integral component of farming systems and thus contribute significantly to food and economic security in developing countries. Current methods of control for trypanosomosis are inadequate to prevent the enormous socioeconomic losses resulting from this disease. A vaccine has been viewed as the most desirable control option. However, the complexity of the parasite's antigenic repertoire made development of a vaccine based on the variable surface glycoprotein coat unlikely. As a result, research is now focused on identifying invariant trypanosome components as potential targets for interrupting infection or infection-mediated disease. Immunosuppression appears to be a nearly universal feature of infection with African trypanosomes and thus may represent an essential element of the host-parasite relationship, possibly by reducing the host's ability to mount a protective immune response. Antibody, T cell and macrophage/monocyte responses of infected cattle are depressed in both trypanosusceptible and trypanotolerant breeds of cattle. This review describes the specific T cell and monocyte/macrophage functions that are altered in trypanosome-infected cattle and compares these disorders with those that have been described in the murine model of trypanosomosis. The identification of parasite factors that induce immunosuppression and the mechanisms that mediate depressed immune responses might suggest novel disease intervention strategies.

Estimated Financial Impact of Trypanosoma vivax on the Brazilian Pantanal and Bolivian Lowlands

The financial impact of the first outbreak of Trypanosoma vivax in the Brazilian Pantanal wetland is estimated. Results are extended to include outbreaks in the Bolivian lowlands providing a notion of the potential influence of the disease and an analytical basis. More than 11 million head of cattle, valued at more than US$3 billion are found in the Brazilian Pantanal and Bolivian lowlands. The total estimated cost of the 1995 outbreak of T. vivax is the sum of the present values of mortality, abortion, and productivity losses and treatment costs, or about 4% of total brood cow value on affected ranches. Had the outbreak gone untreated, the estimated losses would have exceeded 17% of total brood cow value.

Cattle Dung Breeding Diptera in Pastures in Southeastern Brazil: Diversity, Abundance and Seasonallity

Diptera that breed in undisturbed cattle droppings in pastures present great diversity and abundance, and several species are of veterinary importance and may cause economic losses. To survey the diversity, abundance and seasonality of Diptera associated to this microhabitat, 83 samples of 10 dung pats each were taken from April 1992 to April 1994 in the vicinity of São Carlos, State of São Paulo, Southeastern Brazil. A total of 46,135 Diptera belonging to 20 families and at least 51 species were found to breed in the pats. The most abundant and diverse families were Sepsidae, Muscidae, Sarcophagidae and Sphaeroceridae. In general, the abundance was higher from October to March, the warm and wet months. The importance of some Diptera, both as horn fly enemies and as cattle dung decaying agents, is discussed.

Cytotoxicity of three new triazolo-pyrimidine derivatives against the plant trypanosomatid: Phytomonas sp. isolated from Euphorbia characias

There is no effective chemotherapy against diseases caused by Phytomonas sp., a plant trypanosomatid responsible for economic losses in major crops. We tested three triazolo-pyrimidine complexes [two with Pt(II), and another with Ru(III)] against promastigotes of Phytomonas sp. isolated from Euphorbia characias. The incorporation of radiolabelled precursors, ultrastructural alterations and changes in the pattern of metabolite excretion were examined. Different degrees of toxicity were found for each complex: the platinun compound showed an inhibition effect on nucleic acid synthesis, provoking alterations on the levels of mitochondria, nucleus and glycosomes. These results, together with others reported previously in our laboratory about the activity of pyrimidine derivatives, reflect the potential of these compounds as agents in the treatment of Phytomonas sp.

Bovine papillomavirus type 2 detection in the urinary bladder of cattle with chronic enzootic haematuria

The bovine papillomavirus type 2 (BPV-2) involvement in the aetiology of chronic enzootic haematuria associated to bracken fern ingestion has been suggested for a long time. However, a few reports have shown the presence of the BPV-2 in urinary bladder tumors of cattle. The aim of this study was to investigate the presence of the BPV-2 infection in the urinary bladder of cattle with chronic enzootic haematuria in Brazilian cattle herds. Sixty-two urinary bladders were collected from adult cattle in beef herds from the north region of the state of Paraná, Brazil. According to clinical and pathological finds the specimens were distributed in three groups: the group A was constituted by 22 urinary bladders with macroscopic lesions collected at necropsy of cattle with clinical signs of chronic enzootic haematuria; the group B by 30 urinary bladders with macroscopic lesions collected in a slaughterhouse of cows coming from bracken fern-endemic geographical region; and the group C (control) by 10 urinary bladders without macroscopic lesions collected from asymptomatic cattle in a bracken fern-free geographical region. By a semi-nested polymerase chain reaction (PCR) assay, with an internal control, a fragment of the BPV-2 L1 gene with 386 bp length was amplified in 36 (58%) urinary bladder. The rate of BPV-2 positive urinary bladders was 50% (11/22) for group A, 80% (24/30) for group B, and 10% (1/10) for group C (control). The rate of the positive results found in groups A and B that included urinary bladder samples with macroscopic lesions was 67% (35/52) and the detection of the BPV-2 in both groups was significantly higher (P < 0.05) than in the control group. RFLP with Rsa I and Hae III enzymes evaluated the specificity of the BPV-2 amplicons. The PCR internal control that amplified a 626 bp fragment of the ND5 gene of the bovine mitochondrial genome was amplified in all analyzed samples and excluded false-negatives or invalid results in the semi-nested PCR. These results suggest the BPV-2 involvement in the chronic enzootic haematuria aetiology and open the perspective of the development of new strategies for the control of this disease that is the major cause of economical losses in beef herds from many Brazilian geographical regions.

Resistance to experimental autoimmune encephalomyelitis development in Lewis rats from a conventional animal facility

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the brain and spinal cord that is mediated by CD4+ T lymphocytes specific to myelin components. In this study we compared development of EAE in Lewis rats from two colonies, one kept in pathogen-free conditions (CEMIB colony) and the other (Botucatu colony) kept in a conventional animal facility. Female Lewis rats were immunized with 100 µl of an emulsion containing 50 µg of myelin, associated with incomplete Freund's adjuvant plus Mycobacterium butyricum. Animals were daily evaluated for clinical score and weight. CEMIB colony presented high EAE incidence with clinical scores that varied from three to four along with significant weight losses. A variable disease incidence was observed in the Botucatu colony with clinical scores not higher than one and no weight loss. Immunological and histopathological characteristics were also compared after 20 days of immunization. Significant amounts of IFN-gamma, TNF-alpha and IL-10 were induced by myelin in cultures from CEMIB animals but not from the Botucatu colony. Significantly higher levels of anti-myelin IgG1 were detected in the CEMIB colony. Clear histopathological differences were also found. Cervical spinal cord sections from CEMIB animals showed typical perivascular inflammatory foci whereas samples from the Botucatu colony showed a scanty inflammatory infiltration. Helminths were found in animals from Botucatu colony but not, as expected, in the CEMIB pathogen-free animals. As the animals maintained in a conventional animal facility developed a very discrete clinical, and histopathological EAE in comparison to the rats kept in pathogen-free conditions, we believe that environmental factors such as intestinal parasites could underlie this resistance to EAE development, supporting the applicability of the hygiene hypothesis to EAE.

Molecular and morphological characterization of heterorhabditid entomopathogenic nematodes from the tropical rainforest in Brazil

Despite massive losses of primary forest, the Amazonian rainforest remains an extremely rich source of biodiversity. In recent years, entomopathogenic nematodes (EPNs) have been isolated from soil in various parts of the world and used successfully as biological control agents against numerous insect pests. Therefore, a sampling in the rainforest of Monte Negro, Rondônia, Brazil was conducted with the aim of discovering new strains and/or species of EPNs for future development as biological control agents. From 156 soil samples taken at nine collecting sites, 19 isolates were obtained, all of them belonging to the genus Heterorhabditis. Four strains were subjected to detailed morphological and molecular evaluation. Based on morphometrics and internal transcribed spacer (ITS) sequence data, the strains LPP1, LPP2 and LPP4 were identified as Heterorhabditis indica, whereas LPP7 was considered Heterorhabditis baujardi. Comparative analysis of the ITS1 sequence of H. indica and H. baujardi isolates showed a polymorphic site for the restriction enzyme Tth 111 that could be used to distinguish the two species. Consequently, strains LPP1, LPP2, LPP3, LPP4, and LPP9 were identified as H. indica, whereas LPP5, LPP7, LPP8 and LPP10 were identified as H. baujardi.

Molecular characterization of G and P-types bovine rotavirus strains from Goiás, Brazil: high frequency of mixed P-type infections

In this study, 331 samples from calves less than one month old from a dairy herd in the district of Piracanjuba, state of Goiás, Brazil were tested for rotavirus. Thirty-three samples (9.9%) tested positive for rotavirus. Out of those, 31 were submitted to G and P characterization by reverse transcription followed by semi-nested polymerase chain reaction. Two samples were characterized as G6P[1], three as G10P[11] and five as G6P[11]. The majority of the samples (51.6%) displayed multiple P genotypes (P-genotype mixtures), including typical human genotypes P[4] and P[6M], suggesting the occurrence of co-infections and genetic reassortment. Also, the detection of human genotypes in bovine samples may be considered evidence of the zoonotic potential of rotaviruses. To our knowledge, this is the first report of such a high frequency of P genotype mixtures in bovine rotavirus samples. It also increases data on G and P rotavirus genotypes circulating in dairy herds in Brazil and can help in the development of more efficient immunization approaches, thereby controlling infection and reducing economical losses.

Trichomonas vaginalis and Tritrichomonas foetus: interaction with fibroblasts and muscle cells - new insights into parasite-mediated host cell cytotoxicity

Trichomonas vaginalis and Tritrichomonas foetus are parasitic, flagellated protists that inhabit the urogenital tract of humans and bovines, respectively. T. vaginalis causes the most prevalent non-viral sexually transmitted disease worldwide and has been associated with an increased risk for human immunodeficiency virus-1 infection in humans. Infections by T. foetus cause significant losses to the beef industry worldwide due to infertility and spontaneous abortion in cows. Several studies have shown a close association between trichomonads and the epithelium of the urogenital tract. However, little is known concerning the interaction of trichomonads with cells from deeper tissues, such as fibroblasts and muscle cells. Published parasite-host cell interaction studies have reported contradictory results regarding the ability of T. foetus and T. vaginalis to interact with and damage cells of different tissues. In this study, parasite-host cell interactions were examined by culturing primary human fibroblasts obtained from abdominal biopsies performed during plastic surgeries with trichomonads. In addition, mouse 3T3 fibroblasts, primary chick embryo myogenic cells and L6 muscle cells were also used as models of target cells. The parasite-host cell cultures were processed for scanning and transmission electron microscopy and were tested for cell viability and cell death. JC-1 staining, which measures mitochondrial membrane potential, was used to determine whether the parasites induced target cell damage. Terminal deoxynucleotidyltransferase-mediated dUTP nick end labelling staining was used as an indicator of chromatin damage. The colorimetric crystal violet assay was performed to ana-lyse the cytotoxicity induced by the parasite. The results showed that T. foetus and T. vaginalis adhered to and were cytotoxic to both fibroblasts and muscle cells, indicating that trichomonas infection of the connective and muscle tissues is likely to occur; such infections could cause serious risks to the infected host.

Influenza A virus infection of healthy piglets in an abattoir in Brazil: animal-human interface and risk for interspecies transmission

Asymptomatic influenza virus infections in pigs are frequent and the lack of measures for controlling viral spread facilitates the circulation of different virus strains between pigs. The goal of this study was to demonstrate the circulation of influenza A virus strains among asymptomatic piglets in an abattoir in Brazil and discuss the potential public health impacts. Tracheal samples (n = 330) were collected from asymptomatic animals by a veterinarian that also performed visual lung tissue examinations. No slaughtered animals presented with any noticeable macroscopic signs of influenza infection following examination of lung tissues. Samples were then analysed by reverse transcription-polymerase chain reaction that resulted in the identification of 30 (9%) influenza A positive samples. The presence of asymptomatic pig infections suggested that these animals could facilitate virus dissemination and act as a source of infection for the herd, thereby enabling the emergence of influenza outbreaks associated with significant economic losses. Furthermore, the continuous exposure of the farm and abattoir workers to the virus increases the risk for interspecies transmission. Monitoring measures of swine influenza virus infections and vaccination and monitoring of employees for influenza infection should also be considered. In addition regulatory agencies should consider the public health ramifications regarding the potential zoonotic viral transmission between humans and pigs.