Prevalence, diagnostic evaluation, and disease associations of blood-borne pathogens and ticks from domestic dogs and cats across Namibia

Abstract

There is a significant research gap on haemoparasitic infections in small companion animals of Namibia. Often linked to neglected tropical pathogens, these diseases contribute to many clinical cases, with some infections remaining asymptomatic and undetected. Understanding their prevalence and impact is essential for improving diagnostic and treatment approaches in local veterinary care. This study examined the prevalence of selected blood-borne pathogens in domestic, mostly free-roaming dogs and cats across Namibia, using a multi-modal diagnostic approach, and assessed their clinical significance by exploring associations between tick presence, pathogen infection, and disease manifestation. Samples originating from 15 towns across eight regions of Namibia were tested for infectious diseases including Ehrlichia, Anaplasma, Babesia, Hepatozoon, Dirofilaria, Borrelia, feline leukaemia virus, and feline immunodeficiency virus. Diagnostic tools used in evaluation included light microscopy, serology, haematology, biochemistry, quantitative real-time polymerase chain reaction, and Pacific Biosciences microbiome sequencing. In 375 dogs, overall seroprevalence was 64%, with Ehrlichia (59%), Anaplasma (45%), Dirofilaria (2%), and Borrelia (<1%). The qPCR assays detected 54% overall prevalence, mainly Ehrlichia canis (27%), Hepatozoon canis (25%), Anaplasma species (13%), and Babesia vogeli (8%). Microscopy was the least sensitive (11%). Infection rates varied by region, with Kunene and Otjozondjupa highest (75%) and Erongo lowest (38%). Significant associations were found between pathogen infection, tick presence, and abnormal clinical features, including canine ehrlichiosis and tick presence (P = 0.001) and thrombocytopenia (P = 0.022). A contextual, multi-modal diagnostic approach was recommended for guiding responsible treatment strategies in dogs. In 280 cats, pathogen detection rates varied by method: microscopy (5%), serology (42%), and qPCR (27%). Microscopy detected large Babesia-like inclusions (3%), serology identified FIV (4%) and FeLV (40%), while qPCR found E. canis (2%) and H. canis (26%). Associations between tick presence, pathogen infection, and disease manifestation was found, with a notably significant association between H. canis and FeLV infection (P = 0.005). The study underscored the need for appropriate diagnostic testing to inform responsible treatment strategies for Namibian cats. Analysis of the blood microbiomes of Namibian dogs and cats using 16S rRNA gene PacBio long-read sequencing showed that proteobacteria dominated the taxonomic profile, with regional differences in microbial composition. Phylogenetic analysis identified amplicon sequencing variants related to E. canis, A. platys, Mycoplasma species, and an uncultured Bartonella strain. Co-infections, particularly between Ehrlichia, Anaplasma, and Mycoplasma species, were common. While no significant links to disease manifestation were found, qPCR and PacBio results showed strong diagnostic agreement. This was the first amplicon sequence variant approach to a blood microbiome study in Namibian companion animals, highlighting the need for translational research to aid veterinary practitioners. This study provided key insights into prevalence of blood-borne pathogens of Namibian dogs and cats, using various diagnostic modalities and demonstrating several significant associations between pathogen infection, tick presence, and disease manifestation. Furthermore, the results demonstrated only slight agreement between traditional diagnostics and qPCR, but substantial agreement between qPCR and PacBio methods. The results emphasise the need for accurate diagnostic approaches and improved strategies to guide treatment and disease management in companion animals of Namibia.