The importance of the dog (Canis lupus familiaris) in cocoa farms as carriers of helminths potentially transmissible to humans and wildlife in the Southern Bahia, Brazil

Abstract

Domestic dogs (Canis lupus familiaris) can be considered an invasive species as they have been introduced by humans in different parts of the world and represent a risk to wildlife conservation. Large extensions of agroforestry systems, where cocoa is grown under the shade of native trees, contribute to wildlife conservation in southern Bahia, Brazil. However, this system can increase contact between species of the native fauna and domestic dogs, which are frequently taken to the fields by rural workers. The aims of this study were to investigate the presence of domestic dogs inside cocoa agroforestry systems and the occurrence of helminths in dogs from cocoa farms near two protected areas: the Una Biological Reserve (REBIO-Una) and the Serra das Lontras National Park in Una, Bahia. We also investigated general characteristics of the dogs such as age, sex, breed, feeding frequency, vaccination, deworming and others, and evaluated possible risks of wildlife and human contamination by the domestic dog parasites. Camera traps were set up on eight cocoa agroforestry systems and three adjacent forest fragments. For parasitological investigation, fecal samples were collected from domestic dogs that lived on the eight cocoa farms. A total of 539 photos of 12 mammals were registered, of which 15% were of domestic dogs. The parasitological research was carried out with fecal samples from 32 of the 39 dogs that lived in the cocoa farms. We found one genus of cestode, Dipylidium sp. (7.7%), and five genera of nematodes, Ancylostoma sp. (80.7%), Strongyloides sp. (38.4%), Toxocara sp. (30.7%), Spirocerca sp. (15.4%) and Trichuris sp. (11.5%). Regarding animal care, all dogs were in poor body condition, 49% were fed twice a day, 90% defecated in the forest or cocoa agroforestry systems, only 33% were periodically dewormed, 64% were vaccinated against rabies in less than 12 months, and only one dog was vaccinated against other viruses. The results showed that domestic dogs share the same environment as wild animals yet lack some basic health care, increasing the possibility of parasitic transmission between domestic dogs, wildlife and humans from environmental contamination. We highlight the need for responsible pet ownership and the monitoring the health of wild animals and the human population living in this region.

Diversity of helminths with zoonotic potential and molecular characterization of Toxocara canis infecting domestic dogs from locations of Amazon and Atlantic Forest Brazilian biomes

“…The prevalence of gastrointestinal parasites in dogs reported here, mainly hookworms and Toxocara sp., is in line with the findings of other studies that have demonstrated the need for a surveillance program in Brazil, along the lines of One Health concept, for the prevention of zoonotic diseases transmitted by dogs that circulate between domestic and wild areas, in order to avoid possible spillover events (Dantas-Torres & Otranto, 2014;Curi et al, 2017;Silva et al, 2022;Winck et al, 2022).…”

“…Although it has no known zoonotic potential, the nematode T. vulpis is among the most prevalent helminth parasites of domestic dogs with significant frequencies (Figure 2). The notable prevalence of this parasite in dogs is found in other similar studies (Silva et al, 2022;Souza et al, 2023;Ugalde et al, 2023).…”

“…Silva et al (2022) also reported a relatively high prevalence (7.7%) of D. caninum infecting dogs living in the Atlantic Forest biome compared to other parasitological survey studies. It is known that helminth eggs can survive for long periods in moist and shaded soil (Silva et al, 2022). However, more studies are needed to understand the factors that lead to this prevalence in forest areas and the phylogeography of these taxa in Brazil.…”

“…In Brazil, studies of this nature are concentrated in the Southeast region (Dantas-Torres, 2020), making it difficult to truly understand the distribution of these parasites in a country of continental proportions such as Brazil (Dantas-Torres & Otranto, 2014). Data are even scarcer in the case of rural dogs with access to forest areas, which can act as sources of infection in humans and other wild animals (Curi et al, 2017;Silva et al, 2022). In this regard, this study ratifies the circulation of these parasites in Brazil's North region, more specifically in the state of Acre.…”

“…Biogeography studies of small mammals demonstrate this flow of animals during evolutionary history, which probably resulted in the overlap of taxa in these biomes (Costa, 2003). Silva et al (2022) also reported a relatively high prevalence (7.7%) of D. caninum infecting dogs living in the Atlantic Forest biome compared to other parasitological survey studies. It is known that helminth eggs can survive for long periods in moist and shaded soil (Silva et al, 2022).…”