Wolbachia pipientis: Endosymbiont Bacteria of Dirofilaria immitis and its Role in Feline Dirofilariasis

Wolbachia found so far in arthropods (Vieira et al 2015), while subgroups C and D contain the Wolbachia of the Filarial nematodes. Members of subgroup F tend to be found in arthropods, such as termites, and in the nematode Mansonella ozzardi, the causative agent of filariasis in humans (Konecka et al 2019). It is known that W. pipientis manipulates the reproduction of arthropods causing parthenogenesis, cytoplasmic incompatibility, feminization, and finishing with the death of males (Fitzpatrick et al 2019); in filarial nematodes they act as a compulsory mutualism bacterium (Savola et al 2019). This intracellular bacterium is observed in several species of the Onchocercidae family (Momčilović et al 2019), and there is a relationship within the different species of filaria (Savola et al 2019). Within the filarias, they can be found in D. immitis (Marcos et al 2017), D. repens (Savola et al 2019), O. volvulus (de Pinho Mixao et al 2016), B. malyi and B. pahangi. However, some filarial species do not contain it. 18 Species were analyzed showing that 10 of them harbored this endosymbiotic bacterium (Konecka et al 2019). The Wolbachia has also been detected in the different larval stages of D. immitis, the nematode that causes heartworm disease in dogs and cats. There is evidence that this bacterium is transmitted transovarrically to its offspring (Sato et al 2017), since it is observed in oocytes, developing eggs (Diakou et al 2017) and microfilariae of D. immitis (Satranarakun et al 2016) The treatment with antibiotics intervenes with the change of the Description and taxonomy W. pipientis belongs to the sub-group of the species α-proteobacteria (Diakou et al 2019) of the rickettsial order of the Anaplasmataceae group (Diakou et al 2017). Wolbachia is an endosymbiotic bacterium found in more than 20% of all insects (Wang et al 2019), arthropods (Khanmohammadi et al 2019), mosquitoes (Shaikevich et al. 2019), nematodes (Wang et al 2019) and arachnids (Gerth et al, 2017). First described by Venco et al. (2015) in the ovaries and testes of the Culex pipiens mosquito, it was recognized as a Rickettsia until proposed the name of W. pipientis due to its presence in the mosquito C. pipiens and in honor of his collaborator Wolbach. It is a bacteria with similar characteristics to a rickettsiae, dimorphic, with small irregular shapes formed in rods (0.5-1.3 μm in length) and coccoid forms (0.25-0.5 μm in diameter) that exist near large forms (1-1.8 μm diameter), in turn, it presents a level of pleomorphism that increases with the age of the host cell (Satjawongvanit et al 2019). Its cytoplasm consists of ribosomes and nucleic acid fibers. W. pipientis is presented in a three-layer vacuolar envelope. The outermost layer is native to the host followed by the bacterial outer wall and the innermost cell layer, consisting of the plasma membrane of the bacterium (He et al 2018). The type containing W. pipientis is divided into 6 subgroups, subgroups A, B and E containing many of the Abstract. Despite intense research on Feline and Canine Dirofilariosis, Wolbachia pipientis has been ignored for years. W. pipientis is an endosymbiotic bacterium that hosts certain nematodes, including Dirofilaria immitis known as heartworm disease. Feline dirofilariosis is of reserved prognosis due to the nature of the disease; its diagnosis is not exact with conventional methods but the implementation of molecular biology gives a vision for future research on the symbiotic relationship between Wolbachia and Dirofilaria immitis representing an advance in the diagnostic and therapeutic approach. This review discusses the biology of the bacterium, its relationship with dirofilariasis, the current aspects of the role in the pathogenesis of the disease and the molecular mechanisms of detection.