Objective: Investigation on the epidemiology of filariosis due to different filariae that their microfilaria can be found in blood circulation of rural and urban dog ofTabriz.
Design: Cross sectional study.
Animals: Three hundred and fifty five dogs including 198 rural dogs and 159 shep dogs.
Procedure: One mililiter of blood sample was taken and mixed with 9 ml of 2% formaldehyde. After centrifugation in 3000 rpm the sediment was examined microscopicaIly for microfilriae. Statistical analysis: Ch2 and ficsher exact test were used.
Results: Using differential keys for diagniosis of microfilariae, it was found that 48 dogs (13. 44%) harbored either D. immitis or D. reconditum or both of them in their blood. Out of 48 dogs 30 (8.4%) were infected with D.immitis 17 (4.76%) with D.reconditum and 1 with both microfilariae. The ratio between the infection with D. immitis in urban and rural dogs was 4: I (12.6% vs. 3.14%) in contrast to D. reconditllm infection (1.8% vs. 2%) Both were statistically significant (P< O. 0 I and P< 0.05). The rate of infection increased with age and dogs older than 9 year of age were among the highly infected dogs (P< O. 001) with D. immitis (66.7%). There was also a relation between sex and D. immitis infection in urban dog. D.immitis was more prevalent among the male dogs (P< 0.00 I). It was also found that there is a relation between environmental conditions and the infection. The rate of infection with D. immitis was higher than the 3 other regions (P< O. OOI).Although there was a significant relation between race and infection with D. immitis (P< 0.0 I) and native dogs were among the highly infected dogs, but it seems that this factor may be affected by different factors, thus cannot be the regarded as a valid parameter. D. immitis was
coIlected from foxes, wolves and jackals from suburban area of Tabriz. No microfilariae was detected in 2192 mosquitoes.
Clinical implications: Our finding revealed that dogs of Tabriz
either urban or rural, harboured microfilariae of D. immitis and D. reconditllm in their circulating blood. Ecological factors such a humidity, more movemet of sheep dog, the suitable conditions of urban areas for breeding of mosquitoes and that of rural region for tick, caused the more prevalence of D. immitis in urban dogs and D. reconditllln in rural dogs. Again the coIlecton of D. immitis from wild carnivores around Tabriz revealed that this region in one of the endemic areas of Iran was infected with filarial infections, especiaIly D. immitis thus a control program must be carried out for controling mosquitoes intermediate host as well as heartworm disease. J. Fac. Vet. Med. Univ. Tehran. 57,4: 59-63, 2002.