Fine structure of Henneguya pilosa sp. n. (Myxozoa: Myxosporea), parasite of Serrasalmus altuvei (Characidae), in Brazil

Henneguya pilosa sp. n., a new species of myxosporean from the gill filaments of the white piranha, Serrasalmus altuvei Ramirez, 1965 (Characidae), a freshwater teleost fish collected in the Zoological Garden of the city of Teresina (Piauí), Brazil, is described from light and transmission electron microscope observations. This myxosporean produced small plasmodia (up to 0.2 mm in diameter), each one containing all life-cycle stages of the parasite, including numerous spores. The spores, laterally compressed, averaged 54.2 (52.3-56.0) microm in total length and consisted of two unequal valves adhering together along the suture line and two caudal processes. The spore body measured 21.1 (20.0-23.1) microm in length, 5.9 (5.5-6.3) microm in width, and 2.2 (1.9-2.6) microm in thickness. The two equal ellipsoidal polar capsules of 7.4 (7.1-7.6) microm long and 1.2 (1.0-1.3) microm wide possessed a polar filament with 11-12 (rarely 13) turns. All surfaces of the spores were covered with a tightly adherent complex network of numerous densely ramified granulo-fibrillar masses, the longest measuring 1.5 microm long, observed around the caudal processes. The prevalence of infection was 30%. The taxonomic affinities of this parasite with other of the same genus in freshwater South American fish species are discussed.     

Component population study of Acanthocephalus tumescens (Acanthocephala) in fishes from Lake Moreno,Argentina

Seasonal samples of all fish species from Lake Moreno were taken in order to determine the presence of paratenia, to evaluate the status of the hosts and to characterise the transmission of Acanthocephalus tumescens (von Linstow, 1896) at the component population level. Prevalence, mean abundance, mean intensity, numbers of gravid females, relative abundance of the different fish species, relative output of eggs and relative flow rates for each host species were computed. Acanthocephalus tumescens showed low host specificity, successfully parasitizing six out of eight fish species present in the lake. No paratenic infection was registered. If prevalence, mean abundance, and number of gravid females are considered, host species can be placed in a continuum from the most to least suitable as follows: Galaxias platei Steindachner, Diplomystes viedmensis (Mac Donagh), Oncorhynchus mykiss (Walbaum), Salvelinus fontinalis (Mitchill), Percichthys trucha (Cuvier et Valenciennes) and Galaxias maculatus (Jenyns). However, when parasite flow rates and egg output were calculated, including relative abundance of each fish species, the continuum was rearranged as follows: P. trucha, O. mykiss, G. platei / G. maculatus, S. fontinalis and D. viedmensis. The first four species would be the main contributors to the population of A. tumescens in this lake, P. trucha being the major one. Different regulatory and non-regulatory mechanisms are suggested.     

Prevalence of antibodies against Ornithobacterium rhinotracheale in broilers and breeders in Southern Brazil

In this investigation, we determined the prevalence of the Ornithobacerium rhinotracheale (ORT) infection in broilers and broiler breeders in southern Brazil. We also correlated the presence of antibodies in broilers with performance. Sera from 1550 broilers from 50 flocks were collected during the slaughter time in nine companies with federal veterinary inspection of the state of Rio Grande do Sul. Sera from 480 meat-type breeders of 40 flocks from 14 companies in southern Brazil were also analyzed by enzyme-linked immunosorbent assay, and the prevalence of antibodies was determined. The prevalence of ORT antibodies in broiler flocks was 63.83%, but in each individual flock only 6.52% of the birds were positive. The prevalence in broiler breeder flocks was 100.00%, and in each individual flock 94.62% of the birds were positive. There was a positive correlation between the presence of antibodies to ORT and decreased body weight in broilers. There was no significant correlation between presence of antibodies to ORT and age, lineage, efficiency index, feed conversion, and mortality. There was a positive correlation between the presence of respiratory signs and antibodies to ORT, although the reverse correlation was not significant. These results confirm that ORT is present and widespread in broilers and broiler breeders in southern Brazil.     

Larvicidal effects of several chemicals on Strongyloides infective larvae

The larvicidal effects of 11 anthelmintics, 7 pesticides and 4 disinfectants were evaluated with infective larvae of Strongyloides papillosus (SPL) and Strongyloides venezuelensis (SVZ). The lethal concentrations against SPL and SVZ were found to be similar. Three chemicals (dichlorvos, levamisole and trichlorfon) showed highest larvicidal effects. The 50% lethal concentration (LC(50)) values for the three compounds against SPL larvae were 0.08, 0.24, and 0.59 ppm, respectively.     

Disseminated pythiosis in three horses

Three cases of equine subcutaneous pythiosis with dissemination to the internal organs were investigated. The subcutaneous lesions were observed on the mammary gland, nostrils and limbs of the infected horses. Histopathological analysis of the infected tissues revealed a strong eosinophilic reaction, with macrophages, mast cells and giant cells. Sparsely septated hyphal filaments of 4-6 microm diameter were identified in the center of the eosinophilic areas. Specific fluorescent antibody against Pythium insidiosum confirmed the hyphae in the infected tissues in three examined horses. In one of the three cases, the DNA sequences amplified from the infected subcutaneous tissues and internal organs, revealed that P. insidiosum's 18S SSU rDNA amplicons shared 100% identity with those sequences deposit in GenBank. This is the first report confirming by immunochemical and genetic techniques that P. insidiosum can disseminated from superficial to deep structures.     

Occurrence of the temperature-sensitive hemagglutinin among avian Escherichia coli

In this study, we determined the occurrence of the tsh gene among 305 Escherichia coli isolates from chickens by means of the polymerase chain reaction and agglutination of chicken erythrocytes; 200 of those isolates were obtained from chickens with colisepticemia, 52 isolates were from lesions of cellulitis, and 53 were from feces of normal chickens. The tsh gene was found in 79 (39.5%) isolates from colisepticemia, in 10 (19%) cellulitis-derived E. coli isolates, and in two (3.8%) fecal isolates. Among the tsh+ strains, 68 (86%) isolates from colisepticemia and nine (90%) from cellulitis agglutinated chicken erythrocytes in the presence of mannose, after growing the strains on colonization factor antigen agar plates at 26 C, which confirms a correlation between mannose-resistant hemagglutination and expression of hemagglutinin Tsh. These results show, for the first time, the presence of the gene tsh in cellulitis-derived E. coli isolates; the high frequency of this gene among avian pathogenic E. coli isolates in Brazil indicates that its putative role as a virulence factor should be studied more thoroughly.     

Virulence factors of avian pathogenic Escherichia coli isolated from broilers from the south of Brazil

Sixty-three Escherichia coli strains isolated from broilers with respiratory problems were examined for virulence factors, hemolysin synthesis ability, motility, hemagglutination capacity, operon pap presence, colicin production, and serum resistance. The capacity to hemagglutinate guinea pig erythrocytes was found in 53 (84.1%) of the samples, but only 30 (47.6%) agglutinated chicken erythrocytes. D-mannose-sensitive hemagglutination against guinea pig erythrocytes was found in 19 (30.2%) samples and against chicken erythrocytes, in 15 (23.8%) samples, whereas the D-mannose-resistant hemagglutination with guinea pig erythrocytes was found in 34 (54%) samples, and 13 of these (20.6%) showed this characteristic against chicken erythrocytes. Operon pap, P fimbria codifier, was detected in 26 samples in a total of 34 D-mannose-resistant samples. Colicin production was observed in 55 (87.3%) of the strains, and 41.8% presented V colicin production. Of the samples analyzed, 56 (88.9%) presented serum resistance, six (9.5%) were intermediate, and only one (1.6%) was sensitive to the action of the complement. The diversity of virulence profiles detected in the samples in this study explains in part the multifactorial characteristics of avian colibacillosis.     

Evaluation of 65% permethrin spot-on for prevention of canine visceral leishmaniasis: effect on disease prevalence and the vectors (Diptera: Psychodidae) in a hyperendemic area

A study was designed to examine the effect of 65% permethrin spot-on on the prevalence of canine visceral leishmaniasis and the abundance of sand flies in two neighborhoods in Corumbá, Mato Grosso do Sul, Brazil known to have a high prevalence of visceral leishmaniasis. An enrollment survey was conducted to determine the prevalence of visceral leishmaniasis. Area residents were provided with information about the project; the study area was defined, and all dogs (160 in Cristo Redentor and 230 in Popular Velha) identified in the study area were enrolled. Three 65% permethrin spot-on treatments (June 15-25, July 13-15, and August 10-12) were administered to 150, 110, and 99 dogs, respectively, in Popular Velha, according to label recommendations. Dogs in Cristo Redentor were untreated controls. Visceral leishmaniasis was diagnosed periodically by indirect immunofluorescence assay. A reduction in canine visceral leishmaniasis prevalence was observed at the Popular Velha site. The infection rate for treated dogs 1 month following the final treatment was approximately 50% reduced from that observed before treatment(19.3% vs 9.6%). Conversely, the infection rate at the control site was more than 80% higher at the September sampling than that observed pretreatment (4.1% vs 7.4%). Similar numbers of sand flies were captured and identified from both sites throughout the study. The results suggest that regular use of 65% permethrin during months of high risk for canine visceral leishmaniasis can be a useful strategy for reducing the prevalence of this disease in hyperendemic areas. It should be stressed, however, that the success of this strategy depends not only on the efficacy of the product itself but also on the adoption of other control measures and on economic variables, considering the low purchasing power of the populations living in higher-risk neighborhoods.     

Field and laboratory selection of Frankliniella occidentalis (Pergande) for resistance to insecticides

Response of western flower thrips, Frankliniella occidentalis (Pergande), to selection for resistance to insecticides commonly used to control this pest in Murcia (south-east Spain) was studied under field and laboratory conditions. In the field, plots within sweet pepper crops in commercial and experimental greenhouses were treated under different selection strategies: insecticide rotation versus formetanate reiteration, formetanate reiteration versus acrinathrin reiteration, and formetanate reiteration versus methiocarb reiteration. Thrips populations were sampled monthly and bioassayed against methiocarb, methamidophos, acrinathrin, endosulfan, deltamethrin and formetanate. In the laboratory, F occidentalis strains were selected against each insecticide for several generations. To evaluate cross-resistance, each selected strain was bioassayed with the other insecticides. Frankliniella occidentalis populations showed a rapid development of acrinathrin resistance, reaching high levels in field and laboratory conditions. Formetanate and methiocarb resistance were also observed, although development was slower and at moderate levels. Cross-resistances between acrinathrin/deltamethrin and acrinathrin/formetanate were detected under field and laboratory conditions. Formetanate/methiocarb cross-resistance was suspected in laboratory selections, but not in field assays. Simultaneous moderate resistance levels to the three specific insecticides against thrips (formetanate, methiocarb and acrinathrin) were shown in laboratory selection strains, indicating a general mechanism of resistance, probably metabolic.