Molecular Analysis of Canine Filaria and Its Wolbachia Endosymbionts in Domestic Dogs Collected from Two Animal University Hospitals in Bangkok Metropolitan Region, Thailand

Abstract

Canine filariasis is caused by several nematode species, such as Dirofilaria immitis, Dirofilaria repens, Brugia pahangi, Brugia malayi, and Acanthocheilonema reconditum. Zoonotic filariasis is one of the world’s neglected tropical diseases. Since 2000, the World Health Organization (WHO) has promoted a global filarial eradication program to eliminate filariasis by 2020. Apart from vector control strategies, the infection control of reservoir hosts is necessary for more effective filariasis control. In addition, many studies have reported that Wolbachia is necessary for the development, reproduction, and survival of the filarial nematode. Consequently, the use of antibiotics to kill Wolbachia in nematodes has now become an alternative strategy to control filariasis. Previously, a case of subconjunctival dirofilariasis caused by Dirofilaria spp. has been reported in a woman who resides in the center of Bangkok, Thailand. Therefore, our study aimed to principally demonstrate the presence of filarial nematodes and Wolbachia bacteria in blood collected from domestic dogs from the Bangkok Metropolitan Region, Thailand. A total of 57 blood samples from dogs with suspected dirofilariasis who had visited veterinary clinics in Bangkok were collected. The investigations for the presence of microfilaria were carried out by using both microscopic and molecular examinations. PCR was used as the molecular detection method for the filarial nematodes based on the COI and ITS1 regions. The demonstration of Wolbachia was performed using PCR to amplify the FtsZ gene. All positive samples by PCR were then cloned and sequenced. The results showed that the filarial nematodes were detected in 16 samples (28.07%) using microscopic examinations. The molecular detection of filarial species using COI-PCR revealed that 50 samples (87.72%) were positive; these consisted of 33 (57.89%), 13 (22.81%), and 4 (7.02%) samples for D. immitis, B. pahangi, and B. malayi, respectively. While the ITS1-PCR showed that 41 samples (71.93%) were positive—30 samples (52.63%) were identified as containing D. immitis and 11 samples (19.30%) were identified to have B. pahangi, whereas B. malayi was not detected. Forty-seven samples (82.45%) were positive for Wolbachia DNA and the phylogenetic tree of all positive Wolbachia was classified into the supergroup C clade. This study has established fundamental data on filariasis associated with Wolbachia infection in domestic dogs in the Bangkok Metropolitan Region. An extensive survey of dog blood samples would provide valuable epidemiologic data on potential zoonotic filariasis in Thailand. In addition, this information could be used for the future development of more effective prevention and control strategies for canine filariasis in Thailand.

Detection of Canine Vector-Borne Filariasis and Their Wolbachia Endosymbionts in French Guiana

“…This is the first molecular report of filaria and Wolbachia infections from dogs in French Guiana. Dogs are the most implicated reservoir for filariasis [9][10][11]15,17,19]. The control of these vector-borne helminths is based on epidemiological information and the use of adequate diagnostic methods [40].…”

“…This tool had gained an important increase in research area [41,42]. In addition, several studies have recently associated the molecular detection of Wolbachia in the diagnosis of canine filariasis [9,10,27].…”

“…Finally, our results reported the presence of two Wolbachia strains from the clade C and D of filarial nematodes, wherein the first one was clustered with those associated with D. immitis and the second one with those of lymphatic filarial parasites. In terms of host-relationship, Wolbachia strain is filaria species-specific [23], which allows them to serve as a diagnostic target [10,24,45]. Moreover, in heartworm infected dogs and cats, these bacteria are implemented in pulmonary disease [24,25].…”

“…Canids constitute suitable hosts for many filarial parasites of veterinary and human importance, such as the zoonotic Dirofilaria immitis (Leidy 1856), the agent of cardiopulmonary dirofilariasis (also known as heartworm) in dogs and pulmonary dirofilariasis in human [8], D. repens which causes in humans, like in dogs the subcutaneous filariasis [9]. These two species, together with brugian parasites that cause lymphatic filariasis (e.g., Brugia timori, B. malayi and B. pahangi) [10,11], constitute the most thread-like filarial worms causing millions of canine and human cases throughout the world [12][13][14]. These parasites have bloodstream microfilariae and are transmitted by mosquito bites.…”

New Molecular Data on Filaria and its Wolbachia from Red Howler Monkeys (Alouatta macconnelli) in French Guiana—A Preliminary Study

“…DNA, despite the presence of its Wolbachia, could be result to an amicrofilaremic infection due to single sex infection, an earlier infection stage or any other causes. Such inconsistencies were previously reported between Brugia and Dirofilaria species in dogs [63]. Wolbachia-filaria interactions within co-infected hosts are not well understood.…”