Aplicação da reação em cadeia da polimerase (PCR) para a detecção de DNA de Echinococcus sp. em fezes de cães domésticos (Canis familiaris) do estado do Acre, Brasil

Abstract

Echinococcosis is a zoonotic infection in which canids harbor adult tapeworms in the small intestine and ruminants and rodents have the larval stage (metacestode) in the liver and lungs. Humans are incidental hosts. Among the valid species of Echinococcus in Brazil, Echinococcus granulosus senso latu (s.l.) the causative agent of cystic echinococcosis (CE) is common in Rio Grande do Sul, especially on the borders with Argentina and Uruguay. In the life cycle, domestic dogs, cattle and sheep are definitive and intermediate host, respectively. In the other hand, Echinococcus vogeli causes polycystic echinococcosis (PE) and the natural cycle of transmission in northern Brazil enrolls a predator-prey relationship between the bush dog and the paca, the definitive and intermediate hosts, respectively. In addition, a synanthropic cycle is established when human comes back from hunting and feeds domestic dogs with the entrails of slaughtered pacas. Dogs become infected with liver metacestodes and play a role as definitive hosts in a domestic cycle, contaminating the peridomestic environment with parasite eggs eliminated with their feces. In state of Acre, previous cases of infected pacas, clinical cases human of polycystic echinococcosis and positive serology for PE have been reported. The human cases show epidemiological factors associated with PE. However, the role of domestic dogs in the link in the link between human and natural infection cycle involving E. vogeli is little known and applications of molecular methods for assessing infection by E. vogeli in domestic dogs are lacking in literature. This study aimed to analyze samples from dogs feces from Acre for detecting Echinococcus sp. through the PCR technique using the cox 1 gene. Seventy-five fecal samples (14 from Sena Madureira, 06 from Rio Branco, 07 from Bujari, 36 from Xapuri and 12 from Epitaciolândia) were submitted to routine parasitological examination (spontaneous sedimentation). The sediments were also subjected to DNA extraction and each resulting material to PCR. This study showed environmental contamination by feces of dogs in all 44 collection sites and 41.33% of samples were contaminated with helminth eggs in 23 (52.27%) points. A total of 06 samples were positive in the PCR, however, Echinococcus was confirmed only in 02 samples by DNA sequencing. One sample of E. granulosus s.s. (G1) and one of E. vogeli showed 100% homology with the reference sequences deposited in GenBank. This is the first study carried out in northern Brazil to evaluate the occurrence of Echinococcus sp. in domestic dogs; E. vogeli is an expected finding since it is a PE transmission area. E. granulosus s.s. finding, however, is an unexpected one given that the geographical distribution is the southern area in Brazil. From an epidemiological point of view, infected domestic dogs may be a risk factor for echinococcosis transmission, considering the outstanding scenery of both etiological agents.