Janine F. R. Seetahal

Background: Dirofilaria spp. are parasitic filarial nematodes endemic worldwide that infect dogs but are also zoonotic. Traveling dogs may serve as carriers of zoonotic parasites, including Dirofilaria immitis, introducing them to new regions. However, the risks of importation from endemic areas are unknown. Methods: To study seroprevalence in travelling dogs, we first established the signal-to-positive (S/P) cutoffs for the DiroCHEK ^™ ELISA assay (Zoetis) by spectrophotometry at three wavelengths (490, 620, or 650 nm). We also validated the assay for testing serum pools using known D. immitis -positive serum. We tested sera collected from 6699 dogs traveling from 34 countries between September 2022 and December 2023 using the spectrophotometric method. Samples were tested in serum pools initially, with pool sizes ranging from 5 to 15 samples based on reported prevalence. All pools were tested with and without heat treatment to disassociate immune complexes. Where sample numbers were insufficient to form a pool, samples were tested individually without heat treatment. Dogs in pools that tested positive were retested individually without heat treatment. Prevalence was calculated from pooled testing and individual testing results. Results: We tested 649 serum pools, of which 50 heat-treated pools and 11 non-heat-treated pools tested positive spectrophotometrically. Of these 61 positive pools, 7 tested positive in non-heat treated and heat-treated conditions, resulting in 54 unique pools. During re-testing of individual dogs from the positive pools, 31 pools contained dogs infected with D. immitis , while 23 pools had no positive individuals identified, indicating the presence of cross-reactive nematodes or antigen–antibody complexes. The prevalence of D. immitis and cross-reactive nematodes based on pooled testing was 0–5.32%. Due to the unavailability of specific serological tests for cross-reactive nematodes, they were not identified further. The prevalence of D. immitis based on individual testing was 0–11.1%, which was lower than the reported prevalence in their countries of origin. Conclusions: Our findings indicate that traveling dogs may carry D. immitis and cross-reactive nematodes, increasing the risk of introducing these parasites and/or novel parasite genetics to new areas. While pooled testing allows for screening populations rapidly, this methodology may underestimate true prevalence, particularly in low-prevalence regions.

Lyssaviruses are RNA viruses in the Family Rhabdoviridae, Genus Lyssavirus. They represent the causative agents of acute, progressive encephalitis, known historically as rabies. Regardless of specific etiology, their collective viral morphology, biochemistry, pathobiology, associated clinical signs, diagnosis, epizootiology, and management are essentially the same. Despite centuries of clinical recognition, these quintessential neurotropic agents remain significant pathogens today, with substantive consequences to agriculture, public health, and conservation biology. Notably, the singular morbidity caused by lyssaviruses is incurable and constitutes the highest case fatality of any viral disease. All warm-blooded vertebrates are believed to be susceptible. The dog is the only domestic animal that serves as a reservoir, vector, and victim. In contrast, felids are effective vectors, but not reservoirs. All other rabid domestic species, such as livestock, constitute spillover infections, as a bellwether to local lyssavirus activity. Frequently, professional confusion abounds among the veterinary community, because although the viral species Lyssavirus rabies is inarguably the best-known representative in the Genus, at least 20 other recognized or putative members of this monophyletic group are known. Frequently, this is simply overlooked. Moreover, often the ‘taxonomic etiology’ (i.e., ‘Lyssavirus x’) is mistakenly referenced in a biopolitcal context, instead of the obvious clinical illness (i.e., ‘rabies’). Global consternation persists, if localities believe they are ‘disease-free’, when documented lyssaviruses circulate or laboratory-based surveillance is inadequate to support such claims. Understandably, professional chagrin develops when individuals mistake the epidemiological terminology of control, prevention, elimination, etc. Management is not simple, given that the only licensed veterinary and human vaccines are against rabies virus, sensu lato. There are no adequate antiviral drugs for any lyssaviruses or cross-reactive biologics developed against more distantly related viral members. While representative taxa among the mammalian Orders Chiroptera, Carnivora, and Primates exemplify the major global reservoirs, which mammalian species are responsible for the perpetuation of other lyssaviruses remains a seemingly academic curiosity. This zoonosis is neglected. Clearly, with such underlying characteristics as a fundamental ‘disease of nature’, rabies, unlike smallpox and rinderpest, is not a candidate for eradication. With the worldwide zeal to drive human fatalities from canine rabies viruses to zero by the rapidly approaching year 2030, enhanced surveillance and greater introspection of the poorly appreciated burden posed by rabies virus and diverse other lyssaviruses may manifest as an epidemiological luxury to the overall global program of the future.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for COVID-19, has been found to infect various domestic and wild animal species. In this study, convenience serum samples from 575 bison, 180 elk, and 147 samples from various wildlife species collected between 2020 and 2023 from several regions in the United States were analyzed for the presence of SARS-CoV-2-specific antibodies. Two commercial ELISA assays based on the inhibition of the SARS-CoV-2 receptor-binding domain (sVNT) or the nucleocapsid protein (N-ELISA) of SARS-CoV-2 were used. Positive samples from the sVNT were additionally evaluated using a conventional virus neutralization test (VNT). Our results indicated that 1.2% of bison, 2.2% of elk, and 4.1% of the other wildlife species serum samples were seropositive in the sVNT, whereas 4.2% of bison, 3.3% of elk, and 1.4% of the other captive wildlife species serum samples tested positive by the N-ELISA. Among the sVNT serum samples, two samples from bison, one sample from elk, and five serum samples from other wildlife species (one cheetah, one gorilla, two lions, and one hippopotamus) had neutralizing antibody titers in the VNT, indicating these species are susceptible to SARS-CoV-2 infection. These findings highlight the importance of broad surveillance efforts for the effective monitoring of SARS-CoV-2 in non-human hosts.

Movement of animals and plants from mainland populations contributes to the genetic diversity and viability of geographically isolated island biota, but also carries risks of pathogen introductions. The bat fauna of the island of Trinidad reflects species diversity on the neighbouring South American mainland and includes the common vampire bat ( Desmodus rotundus) . We determined relationships between Trinidad and mainland vampire bat populations and the extent of mainland-island movement by comparing the genetic structure (nuclear and mitochondrial) and morphology of the Trinidadian D. rotundus population to populations in neighbouring regions of the South American mainland and estimating evolutionary histories and patterns of gene flow. Results indicate that Trinidadian D. rotundus are genetically and morphologically distinct from mainland populations, although limited unidirectional male-biased mainland to island gene flow occurs at an estimated rate of 3.3 migrants per year. Two geographically-defined Desmodus cytochrome b clades were identified within Trinidad (i.e., one restricted to the South-Western peninsula which grouped with Venezuelan sequences and the other found throughout the rest of the island which grouped with sequences from Suriname and Guyana) suggesting long-standing female philopatry. The geographic distribution of these clades mirrors that of two previously identified geographically defined rabies virus (RABV) lineages introduced to Trinidad from the mainland. This finding suggests that bat dispersals and RABV introductions occur via both the northern and south-western island peninsulas, with subsequent male-driven intra-island viral spread enabled by bat nuclear homogeneity of these populations. These study findings will contribute to the development of contemporary evidence-based vampire bat population control and rabies prevention programs within island populations.