Canine filariasis in the Amazon: Species diversity and epidemiology of these emergent and neglected zoonoses

Abstract

Dirofilaria immitis and Acanthocheilonema reconditum are common parasites in dogs but have also been reported parasitizing humans. The differential diagnosis and epidemiological evaluation of these zoonoses are important to the development of efficient public health policies and control strategies. The purpose of this study was to carry out an epidemiological survey by using molecular methods for the specific identification of filarid parasites of domestic dogs in the Marajó mesoregion, State of Pará (PA), Brazil. A total of 418 canine blood samples from Marajó mesoregion (Northern Brazil) were collected, submitted to DNA extraction, polymerase chain reaction (PCR) with "pan filarial" primer, subsequent sequencing and sequence analysis using BLASTn software comparison with previously deposited sequences in GenBank. After that, a phylogenetic analysis by Maximum Parsimony was performed to aid the specific diagnosis. The obtained sequences showed the occurrence of 9 (2.15%) dogs infected with D. immitis and 30 (7.18%) by A. reconditum, with a confidence interval of 95%, there were no cases of co-infection. We observed that male dogs were more likely to D. immits and A. reconditum infection. However, age was not significant to both infections. This study reports for the first time the occurrence of A. reconditum in the northern region of Brazil and confirmed the presence of D. immitis in the Marajó mesoregion.

Fig 1. Phylogeny of filarid of the Marajó mesoregion.

The cladogram was inferred using the Maximum Parsimony method. It contains a length of 266, the consistency index is 0.614458 and the retention index is 0.872170. The Bootstrap is indicated next to the knots of the branches. The sequence of the obtained samples were grouped in two clades: In clade I, 30 sequences of the municipalities Soure, Chaves, Portel, Anajás São Sebastião da Boa Vista formed a politomy with A. reconditum (AF217801.2), with Bootstrap of 73%. Clade II is composed by 9 sequences of Soure and Chaves municipalities, which form a polytomy with D. immitis (EU182330.1) withal 83% of Bootsrap. The other filarid sequences remained in isolated branches: D. dracunculoides (DQ018785.1) as a brother group of A. reconditum (Bootstrap 96%) and D. repens (AY693808.1) most related to D. immitis (Bootstrap 96%). A. lumbricoides (AB571301.1) and T. trichiura (KC877992.1) are the outgroup.