Journal of Wildlife Diseases最新文献

Sarcoptic mange (SM), caused by the mite Sarcoptes scabiei, is a globally distributed disease affecting a broad range of hosts and posing a potential threat to wildlife. However, its full ecologic impact remains unclear. This study investigates SM occurrence in two native fox species (Lycalopex spp.) in rural central Chile, exploring its association with macrohabitat types, land covers, domestic dogs, and human presence. Fieldwork was conducted across three rural sites (<56 km apart), representing distinct macrohabitats: exotic monoculture tree plantations (Alto Colorado) and two native Mediterranean coastal forest sites, La Estrella (thorn shrubland) and Callihue (sclerophyllous forest). At each site, 10 camera traps were deployed within 100-ha grids for 13 mo. Foxes were detected in all stations, and individuals showing lesions consistent with SM (SM-foxes) were found in 24 of 30 stations, accounting for 329 of 3,140 fox images (10.4% observed prevalence). Domestic dogs were recorded at 28 stations, detected up to 7.9 km from human settlements. In our fine-scale approach, foxes, SM-foxes, and dogs were present across all macrohabitats and land covers, tending to be more abundant in native landscapes. The occurrence of SM was weakly associated with human presence and, to a lesser extent, with domestic dogs, the latter of which nonetheless remain the most plausible original source of SM in the region. In general, SM occurrence, foxes, and domestic dogs were more frequent closer to human settlements and farther from urban areas, reflecting a complex association with human presence. Human settlements were not consistently related to altered macrohabitats such as exotic plantations. Sarcoptes scabiei circulation is probably maintained through both direct and indirect contact, involving occasional spillover from dogs, prey, and infected carcasses. These findings underscore the importance of rural areas as hotspots for dogs-fox interactions and highlight the relevance of understanding fine-scale pathogen dynamics for wildlife conservation.

This report describes highly pathogenic avian influenza virus (HPAI) H5N1 infections in carnivores in Alaska, USA between 2022 and 2024, including a black bear (Ursus americanus), a brown bear (Ursus arctos), and the first known report of HPAI in an ermine (Mustela ermina). The two bears were cubs, and the ermine was a young adult. The black bear and ermine were euthanized after demonstrating neurologic signs, including circling, blindness, ataxia, or seizures. The brown bear was found dead. Gross lesions included swelling and congestion of the brain in both bears. Microscopically, all three individuals exhibited severe, nonsuppurative necrotizing meningoencephalitis, which was most prominent in the gray matter. Nonneuropathic microscopic lesions shared between both bears were multifocal random hepatic necrosis with lymphoplasmacytic hepatitis and mild interstitial pneumonia with bronchitis. The spectrum of additional lesions in individual animals consisted of acute necrosis within multiple other organs, including skeletal muscle, pancreas, kidney, retina, adrenal glands, and intestine. Immunohistochemistry demonstrated positive staining within neurons and glial cells in the brain, enterocytes and neurons of the myenteric plexus in the intestine, rare bronchiolar epithelial cells, renal tubular epithelial cells, and myocyte nuclei. Two HPAI-positive red foxes (Vulpes vulpes) and one positive Arctic fox (Vulpes lagopus) with incomplete histopathology are briefly discussed, as they demonstrate potential for co-infections with HPAI and canine distemper virus or rabies virus.

Mortalities in Black Vultures (Coragyps atratus) caused by A/goose/Guangdong/1/1996 2.3.4.4b lineage highly pathogenic (HP) influenza A virus (IAV) H5N1 (HP H5N1) were detected in Florida, USA, on 14 February 2022. By the end of 2022, at least 2,674 and 5,707 deaths where HP H5N1 infection was confirmed or suspected had been documented in Florida and the USA as a whole, respectively. Reported vulture mortalities at die-off locations nationwide ranged from 1 to 700. In Florida and Pennsylvania, USA, antibodies to both H5 and N1 subtypes of IAV were detected in apparently healthy Black Vultures sampled ≤12 mo after mortality events. Antibodies to these subtypes were not detected in Black Vultures at sites in Kentucky and Tennessee, USA, where HP H5N1 was not detected, nor in Pennsylvania vultures sampled before HP H5N1 introduction into North America. Infections in vultures probably originated through scavenging of infected bird carcasses, but once in the vulture population, HP H5N1 infections may have been maintained by conspecific scavenging. Black Vultures can serve as an indicator species for HP H5N1 in North America, and they may sustain an outbreak after infection rates have declined in other species.

Apicomplexans are endoparasites that infect various animals, including humans, causing significant diseases such as malaria, babesiosis, cryptosporidiosis, neosporosis, and toxoplasmosis. Toxoplasmosis, caused by Toxoplasma gondii, is a notable public health concern due to its severe effects on pregnant women and immunocompromised individuals. Infection routes include ingestion of oocysts from definitive hosts (felines) or consumption of contaminated meat. Neosporosis, caused by Neospora caninum, causes reproductive issues and significant economic losses in domestic cattle (Bos taurus). Wildlife plays a crucial role in the life cycles of these parasites, with species such as wild boar (Sus scrofa) and axis deer (Axis axis) acting as reservoirs. These ungulate species can affect livestock production systems and public health, particularly in regions like Latin America where they are invasive. Understanding the seroprevalence and transmission dynamics of these parasites in wildlife is vital for developing effective control measures. During 2020-23, 254 wild boar and 90 axis deer blood samples were collected from eight and five departments in Uruguay, respectively. Serologic tests for T. gondii and N. caninum antibodies were conducted using ELISA, with further confirmation of N. caninum antibodies through western blotting. Seroprevalence values of T. gondii were mean 47.7% in wild boars and mean 8.4% in axis deer; whereas N. caninum was more prevalent in axis deer (mean 49.8%) than in wild boars (mean 0.7%). Detection of antibodies against both pathogens in a single individual occurred occasionally. These findings suggest that wild boar and axis deer may play significant roles in maintaining and amplifying T. gondii or N. caninum (or both) infections in Uruguay, and underscore the need for targeted control strategies to mitigate the spread of these pathogens, which have implications for both livestock health and public health.

Streptococcus equi ssp. zooepidemicus is a zoonotic bacterium known to cause severe respiratory tract infections in primates, and most documented mortality episodes occur in captivity. Here we report a mass mortality event in a wild population of long-tailed macaques (Macaca fascicularis) inhabiting an urban mosaic habitat in central Bali, Indonesia, and describe the demographic impact and clinical patterns of the outbreak. Mortality was observed in three of the nine social groups that shared overlapping ranges, and the infection spread progressively over time. Clinical signs included lethargy, respiratory distress, and locomotion disorders. Over a 2-mo period during March-May 2022, 170 carcasses were found. Demographic surveys revealed a mortality rate ranging from 16% to 53% among the three affected groups. Adult females and adult males were the most affected age-sex classes, representing 36% and 35% of the carcasses found, respectively. Necropsy findings from four individuals, combined with bacteriological culture, histopathology, qPCR, and 16S rRNA metabarcoding analysis, all suggested Streptococcus equi ssp. zooepidemicus as the most likely causative agent. Similar streptococcal outbreaks had occurred in this population in 1994 and 2012, raising concerns about the recurrent introduction of the bacterium or potential reservoirs either within or outside the macaque population. The recurrence of Streptococcus equi ssp. zooepidemicus outbreaks in this population highlights the impact of lethal bacterial epidemics in wild primates, which remain poorly documented. Strengthening long-term surveillance, including noninvasive serological monitoring, is essential for better understanding infection dynamics and improving conservation strategies.

Drug-induced hypoxemia can occur with the immobilization of free-living moose (Alces alces). We describe the physiologic response of 12 adult females immobilized with thiafentanil and xylazine and exhibiting clinical signs of hypoxemia before (pretreatment) and after (posttreatment) nasal oxygen supplementation (4 L/min) with or without intravenous doxapram.

In 2021-22, clade 2.3.4.4b highly pathogenic avian influenza (HPAI) viruses were introduced by wild birds into North America, leading to geographically widespread disease. In response to HPAI outbreaks throughout late 2021 and early 2022, we recorded observations of sick and dead birds, estimated abundance of carcasses, collected swab and sera samples to detect viruses, and monitored bird nesting on the Yukon-Kuskokwim Delta region of Alaska to document potential effects of disease. Thirty-six reports of sick and dead birds were registered across the region. Nineteen carcasses were opportunistically collected for diagnostic testing, of which 12 were confirmed to be infected with clade 2.3.4.4b HPAI viruses. Carcass abundance estimates from line-distance sampling provided evidence that the most common species of dead birds from the western Yukon-Kuskokwim Delta region were Cackling Goose (Branta hutchinsii minima), Glaucous Gull (Larus hyperboreus), and Black Brant (Branta bernicla nigricans). Only one paired cloacal and oropharyngeal swab sample from a Northern Pintail (Anas acuta) tested positive for clade 2.3.4.4b HPAI virus, out of 464 live-captured duck and goose samples. Of 195 sera samples from waterfowl screened for antibodies reactive to influenza A viruses, antibodies were found in 41-98% of samples collected from Emperor Goose (Anser canagicus), Cackling Goose, Black Brant, and Spectacled Eider (Somateria fischeri). In addition, 15-98% of the same sera samples were reactive to a clade 2.3.4.4b H5 antigen. Fewer Black Brant and Emperor Goose nests were found on long-term study plots during 2022 than in previous years. Collectively, we found that HPAI viruses affected at least seven species of wild birds inhabiting the region during 2022. The full scope of impacts of HPAI at this location during 2022 is unknown, but our data indicate that acute effects to avian population health on the Yukon-Kuskokwim Delta region were likely modest.

In Costa Rica, human-tapir conflicts are increasing, including disease transmission, as Baird's tapirs (Tapirus bairdii) move into human-altered landscapes. We investigated the death of a wild male tapir, identifying a systemic Actinomyces israelii infection. The potential of this pathogen being an emerging health threat for tapir conservation warrants further study.

Few studies exist in which host-pathogen systems have been studied within months of their emergence and followed for many years, making it possible to test the virulence-transmission hypothesis and to determine if a pathogen becomes more or less virulent over time. Around 1994 the bacterium Mycoplasma gallisepticum jumped from poultry to House Finches (Haemorhous mexicanus) and other wild birds in the US. Bacterial virulence increased as it rapidly spread across eastern North America, causing House Finch abundance to decline by half. The new M. gallisepticum variants that eventually colonized the western US had lost a substantial part of their genome and had a reduced virulence. In our study, initial survival of M. gallisepticum was lower in eastern US than in western US isolates, and birds with a higher bacterial load showed higher transmission rates, but this relationship differed between birds inoculated with eastern versus western isolates. Western isolates were less pathogenic (similar pathogen loads caused less-severe disease) than eastern isolates and had lower transmission rates for a given bacterial load. Our study provides insights into how pathogens spreading after a host shift and across a continent may respond to novel evolutionary pressures in diverse ways.

Amphibians are experiencing extinction rates over 200 times the background extinction rate. One emerging infectious disease contributing to amphibian declines is caused by the fungal pathogen Batrachochytrium salamandrivorans (Bsal), which has caused mass die-offs of fire salamanders (Salamandra salamandra) in Europe and could pose a major threat to North American salamander biodiversity if introduced to the continent. A recent study investigated the effects of pathogen dose and environmental temperature on Bsal chytridiomycosis disease progression in wild-caught Notophthalmus viridescens (eastern newts). During that study, necropsy and histologic examination revealed that many newts were infected with multiple parasites. We performed a retrospective analysis on the 41 eastern newts from that study to evaluate whether parasite load was related to Bsal load, environmental temperature, or host survival. In this study 34% (15/41) of newts were infected with nematodes and 22% (9/41) were infected with protozoans. Nematode loads were greatest in newts held at cooler temperatures. Additionally, there was a significant correlation between the overall parasite load and the survival time of newts infected with Bsal. Our results suggest that environmental temperature and parasite infection may interact to increase infection tolerance, which is consistent with recent results reported for Batrachochytrium dendrobatidis. Our results highlight the importance of studying micro- and macroparasite interactions and their possible impacts on host survival.