Survey of canine heartworm in the city of Recife, Pernambuco, Brazil.
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Six hundred and eleven random-source dogs (338 male, 273 female) one year of age or older, from six sections of the city of Recife, Pernambuco, were examined antemortem for circulating microfilariae Dirofilaria immitis and Dipetalonema reconditum adult heartworm (D. immitis) antigen, and examined postmortem for adult heartworms. The prevalence of heartworm infection was 2.3% (14/611), as determined by necropsy for adult worms, and 1% (6/611) had circulating microfilariae of D. immitis; thus, 57.1% of the heartworm-infected dogs had occult infections. The results of serological testing indicated that 1.3% (8/611) of the dogs were positive for adult heartworm antigen. A total of 42 (6.9%) of the dogs had microfilariae of D. reconditum; 40 of these had only D. reconditum and two additional dogs had microfilariae of both species, D. immitis and D. reconditum. (+info)
Vector competence of Culex quinquefasciatus say from different regions of Brazil to Dirofilaria immitis.
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The vector competence of Culex quinquefasciatus from five localities in Brazil to Dirofilaria immitis was evaluated experimentally. Females from each locality were fed on an infected dog ( approximately 6 microfilariae/microl blood). A sample of blood fed mosquitoes were dissected approximately 1 h after blood meal. These results demonstrated that all had ingested microfilariae (mean, 4.8 to 24.6 microfilariae/mosquito). Fifteen days after the infected blood meal, the infection and infective rates were low in all populations of Cx. quinquefasciatus. The mean number of infective larvae detected in the head and proboscis of these mosquitoes was 1-1.5. The vector efficiency, the number of microfilariae ingested/number of infective larvae, was low for all populations of Cx. quinquefasciatus. However, the survival rate for all populations was high (range 50-75%). The survival rate of Aedes aegypti assayed simultaneously for comparison was low (24.7%), while the vector efficiency was much higher than for Cx. quinquefasciatus. These data suggest that the vector competence of all assayed populations of Cx. quinquefasciatus to D. immitis in Brazil is similar and that this species is a secondary vector due to its low susceptibility. Nevertheless, vector capacity may vary between populations due to differences in biting frequency on dogs that has been reported in Brazil. (+info)
Abnormal distribution of anionic sites in the glomerular basement membrane in glomerulonephritis of dogs infected with Dirofilaria immitis.
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Ultrastructural alteration of anionic sites (ASs) in the glomerular basement membrane (GBM) was studied in glomerulonephritis characterized by linear capillary IgG deposition in four dogs infected with Dirofilaria immitis and two normal control dogs using polyethyleneimine. ASs were identified as small dense particles distributed regularly in the lamina rara externa (LRE), but there were no ASs in the lamina densa (LD) of the GBM of the control dogs. In the glomeruli of the infected dogs, ASs were distributed regularly or irregularly in the thickened LD. ASs were in addition localized over the characteristic continuous bands of subendothelial dense deposits. The number of ASs of the LRE increased in all four infected cases as compared to the controls (p<0.01). (+info)
Canine heartworm testing in Canada: are we being effective?
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Mass testing of dogs in Canada for the presence of Dirofilaria immitis has been ongoing since 1977. Since that time, there have also been changes in the diagnostic tests available to detect the presence of heartworm and changes in the therapy for heartworm, which necessitate a reevaluation of heartworm screening as currently practiced in Canada. The principles of evidence-based medicine were used to determine the prevalence of heartworm infection in various dog populations, and the effectiveness of screening these populations. The annual surveys of heartworm testing have shown that Canada is a low prevalence area (0.16%), with most of the test-positive dogs located in southern Ontario (0.19%), southern Manitoba (0.18%), southern Quebec (0.09%), and the southern Okanagan Valley (0.04%). Foci of higher prevalence are found within these 4 main geographic areas. Furthermore, the prevalence of heartworm infection is higher in the population of dogs not on preventative medication (0.62%), when compared to the population of dogs on preventative medication (0.04%). The evidence indicates that a heartworm diagnostic test applied to an asymptomatic dog on preventative medication contributes little information regarding the heartworm infection status of that dog. However, testing of a dog characterized as being high risk will provide clinically useful information. Recommendations regarding the testing of dogs for heartworm in Canada are derived on the basis of available evidence. (+info)
Human antibody response to a 56-kDa purified excretory/secretory product of Dirofilaria immitis.
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Canine dirofilariasis is widespread in urban areas of central and northern Colombia. Previously we detected specific antibodies against complex antigens from Dirofilaria immitis adult worms in individuals from an isolated Tikuna Indian community in the Colombian Amazon. In this study a 56 kDa polypeptide from the adult D. immitis excretory/secretory (E/S) products is identified by Western blot, isolated by elution from polyacrilamide gels and applied in an ELISA-based test for the detection of specific IgG. Eleven of 74 serum samples analysed were positive by ELISADi56. Positive individuals came from five different areas of Colombia. The highest number of positives was found in the Amazon (4), followed by Bogota (3). The physicians of the area must be alerted regarding the existence of human D. immitis infections and include dirofilariasis in the differential diagnosis of pulmonary nodules. (+info)
Antigenic role of the endosymbionts of filarial nematodes: IgG response against the Wolbachia surface protein in cats infected with Dirofilaria immitis.
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Filarial nematodes harbour intracellular endosymbiotic bacteria, which have been assigned to the genus Wolbachia. These bacteria appear to play an important role in the pathogenesis of filarial diseases through their lipopolysaccharides. In view of the presence of Wolbachia endosymbionts in the body of filarial nematodes, one might also expect that proteins from these bacteria play an antigenic role in humans and animals affected by filariases. To test this hypothesis, we produced in recombinant form the surface protein WSP and a portion of the cell-cycle protein FTSZ from the Wolbachia of Dirofilaria immitis. Western immunoblot assays were then performed using cat sera to test the immunogenicity of these proteins. Sera were collected from owners' cats, which were either sero-negative or sero-positive for D. immitis and from cats before and after experimental infection with D. immitis. FTSZ was recognized in Western blots by sera from both positive and negative cats and from both uninfected and experimentally infected cats. WSP was recognized only by sera from positive cats and from cats experimentally infected with D. immitis; this protein was not recognized by sera from negative cats and from cats before experimental infection with D. immitis. The results of Western blot assays on WSP thus support the hypothesis that infection with filarial nematodes induces the production of antibodies against Wolbachia proteins. (+info)
IgG response against infective larvae of Dirofilaria immitis in experimentally infected cats.
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Somatic antigens from third stage larvae of Dirofilaria immitis (SL3) were used to detect IgG response against heartworm infection in 8 experimentally infected cats. A moderate specific anti-SL3 IgG response was found one month post-infection. Afterwards, antibodies decreased reaching a basal level 4 months post-infection and remained at this level until the end of the study. 6 months post-infection. Western blot analysis showed specific recognition of polypeptides of 79, 73, 60, 52, 40 and 39 kDa by sera from infected cats 1 month post-infection, but not by sera taken prior to the infection. The low antigenicity of the SL3 antigen in the cat should allow the parasite to escape the host's immune response. (+info)
Hemodynamic alterations in dogs with shock induced by intravenous injection of heartworm extract.
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To elucidate one way of the shock mechanisms, the hemodynamic alterations were examined in 7 dogs with heartworm (HW) extract-induced shock. The first alteration observed after injection of HW extract was a decrease in right ventricular end-diastolic pressure (RVEDP). After that, left ventricular (LV) end-diastolic pressure, LV systolic pressure, and LV dp/dt fell significantly, followed by a decrease in the cardiac output of all dogs to below the detectable level (1.00 l/min). Since RVEDP depends on blood flow into the right ventricle, the decrease in RVEDP means a reduction in venous return. Therefore, this study showed that the first trigger of a decrease in blood pressure in HW extract-induced shock is the reduction in venous return. (+info)