Citation: Luong, N.H.; Kamyingkird, K.; Thammasonthijarern, N.; Phasuk, J.; Nimsuphan, B.; Pattanatanang, K.; Chimnoi, W.; Kengradomkij, C.; Klinkaew, N.; Inpankaew, T. Companion Vector-Borne Pathogens and Associated Risk Factors in Apparently Healthy Pet Animals (Dogs and Cats) in Khukhot City Municipality, Pathum Thani Province, Thailand. Pathogens 2023, 12, 391. https://doi.org/10.3390/ pathogens12030391 Academic Editor: José A. Oteo Received: 29 December 2022 Revised: 14 February 2023 Accepted: 24 February 2023 Published: 1 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). pathogens Article Companion Vector-Borne Pathogens and Associated Risk Factors in Apparently Healthy Pet Animals (Dogs and Cats) in Khukhot City Municipality, Pathum Thani Province, Thailand Nam Hung Luong, Ketsarin Kamyingkird, Nipa Thammasonthijarern, Jumnongjit Phasuk, Burin Nimsuphan, Khampee Pattanatanang, Wissanuwat Chimnoi, Chanya Kengradomkij, Nutsuda Klinkaew and Tawin Inpankaew * Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand * Correspondence: tawin.i@ku.th Abstract: Pet animals (dogs and cats) can be infected with several companion vector-borne pathogens (CVBPs). Morbidity and mortality have been reported in pet animals due to CVBP infections. Pet animals living in close proximity to humans are able to transmit zoonotic pathogens. This study used molecular techniques to investigate the prevalence of CVBPs in apparently healthy pet animals (dogs and cats) from Khukhot City Municipality, Pathum Thani province, Thailand. In total, 210 blood samples were randomly collected from 95 dogs and 115 cats for the detection of seven companion vector-borne pathogens (Anaplasma, Babesia, Bartonella, Ehrlichia, Hepatozoon, Mycoplasma, and Rickettsia) using polymerase chain reaction. The results showed that 10.5% (22/210) of apparently healthy pet animals were infected with at least one pathogen, comprising 6 dogs (6.3% of all dogs tested) and 16 cats (13.9% of all cats tested). Ehrlichia (6.3%) was present only in dogs; furthermore, 1.1% of the dogs were positive for Anaplasma. There was one dog case co-infected with two pathogens (1.1%). In cats, Mycoplasma (9.6%) was the predominant CVBP, followed by Rickettsia (4.4%). The DNA sequences of all positive animals were 97–99% homologous to those found in the GenBank™ database for all CVBPs identified, namely Ehrlichia canis, Anaplasma platys, Rickettsia felis, Mycoplasma haemofelis, and Candidatus Mycoplasma haemominutum. Additionally, the risk of infection with CVBPs in pets was significantly associated with age, with young dogs more likely to be infected with CVBPs than adult dogs (OR 8.5, 95% CI 1.4–50.1, p = 0.006), while adult cats were more likely to be infected with CVBPs than young cats (OR 3.8, 95% CI 1.0–14.0, p = 0.038). The detection of CVBPs demonstrated the potential risk of infection that may occur in apparently healthy pet animals in Pathum Thani province. These results confirmed that apparently healthy pet animals may still be at risk of vector-borne infections and could maintain the infection cycle in pet populations. Furthermore, sampling a greater number of apparently healthy pet animals may disclose predictors of CVBP positivity in domesticated animals in this area. Keywords: companion vector-borne pathogens; apparently healthy; domesticated animals; Thailand 1. Introduction Companion vector-borne diseases (CVBDs) are illnesses that are transmitted to an- imals, including pets, by vectors such as ticks, fleas, mosquitoes, and sandflies. These diseases are a growing medical concern worldwide [1]. Pets, especially dogs and cats, can play a significant part in the transmission of CVBDs to humans due to the close and often shared living environments between pets and their owners. Additionally, socio-economic factors, such as poverty and poor living conditions, can increase the risk of the pet-to- human transmission of CVBDs [2]. Ticks and fleas are considered the main vectors carrying many companion vector-borne pathogens (CVBPs) and causing tick-borne and flea-borne diseases in pets [3]. Apicomplexan protozoans (Babesia and Hepatozoon) and Alphapro- teobacteria (Anaplasma and Ehrlichia) are common CVBDs causing illness in dogs [4]. In Pathogens 2023, 12, 391. https://doi.org/10.3390/pathogens12030391 https://www.mdpi.com/journal/pathogens