Highly Pathogenic Avian Influenza A(H5N1) Virus Clade 2.3.4.4b Infections in Wild Terrestrial Mammals, United States, 2022.

We describe the pathology of natural infection with highly pathogenic avian influenza A(H5N1) virus of Eurasian lineage Goose/Guangdong clade 2.3.4.4b in 67 wild terrestrial mammals throughout the United States during April 1‒July 21, 2022. Affected mammals include 50 red foxes (Vulpes vulpes), 6 striped skunks (Mephitis mephitis), 4 raccoons (Procyon lotor), 2 bobcats (Lynx rufus), 2 Virginia opossums (Didelphis virginiana), 1 coyote (Canis latrans), 1 fisher (Pekania pennanti), and 1 gray fox (Urocyon cinereoargenteus). Infected mammals showed primarily neurologic signs. Necrotizing meningoencephalitis, interstitial pneumonia, and myocardial necrosis were the most common lesions; however, species variations in lesion distribution were observed. Genotype analysis of sequences from 48 animals indicates that these cases represent spillover infections from wild birds.

GEOGRAPHIC SPREAD OF CANINE DISTEMPER IN WILD CARNIVORES IN MICHIGAN, USA: PATHOLOGY AND EPIDEMIOLOGY, 2008-18.

Canine distemper is a widespread disease affecting both domestic and wild carnivores. This investigation of the geographic distribution, wildlife species infected, and relative prevalence rates was conducted over an 11-yr period and helps to document the disease spread, most highly infected wildlife species, and histologic lesions. Animals were collected as found dead, hunter and trapper harvested, and euthanized for displaying signs of abnormal behavior or neurologic disease. This disease appeared to spread from the Lower Peninsula of Michigan into the Upper Peninsula, was most frequently documented in raccoons (Procyon lotor), striped skunks (Mephitis mephitis), and gray fox (Urocyon cinereoargenteus), but also involved additional wildlife species. Three unique wildlife virus strains were identified. Two of these grouped within a separate subclade of the America 2 lineage. A third strain appeared to be a unique sequence type that is not associated with any existing subclade of America 2. We recommend the combined use of routine histology and immunohistochemical staining to confirm the diagnosis, and further recommend that both the lungs and spleen be collected as the optimal tissues to utilize for surveillance purposes.

Distribution of canine distemper virus and nectin-4 in raccoon (Procyon lotor) skin.

Raccoons (Procyon lotor) are abundant in urban/wildland interfaces and are key sources of canine distemper virus (CDV) outbreaks in domestic, zoo, and free-ranging wildlife species. CDV is pantropic, which provides multiple potential routes of transmission (urine, respiratory secretions, feces), but the specific role of skin as a target of infection, as a diagnostic sample, or as a potential source of environmental persistence and transmission is unknown. We have characterized the distribution of CDV and its known receptor, nectin-4, in skin samples of 36 raccoons. Even with skin samples that were grossly and histologically normal, immunohistochemistry of skin was useful in the diagnosis of CDV infection, which was found in both epithelium and endothelium. Nectin-4 was codistributed with cellular targets of viral infection. Skin secretions, shed keratinocytes, and hair of CDV infected raccoons are all potential environmental fomites.

Eastern Equine Encephalomyelitis in Michigan: Historical Review of Equine, Human, and Wildlife Involvement, Epidemiology, Vector Associations, and Factors Contributing to Endemicity.

Eastern equine encephalomyelitis (EEE) is a mosquito-borne viral disease that is an emerging public health concern in the state of Michigan. Although Michigan has one of the highest incidence rates of EEE in the United States, much of the information known about cases in humans, equines, and other animals residing in Michigan is unpublished. This article summarizes such information and explores spatial trends in the historic distribution of EEE in Michigan. Outbreaks in Michigan have occurred over an 80-yr interval, involving only horses in 1942-1943 and 1973-1976, and then episodically from 1980 to 2020, and involving horses, humans, and wild and domestic animals. An estimated 1,036 equine cases (confirmed and suspected) and 36 confirmed human cases have occurred, including 10 in 2019 (6 deaths) and 4 in 2020 (2 deaths). Human cases ranged in age from 1 to 81 yr; 70% were male, and fatality rate of 34.3%. Equine and human cases occurred from July to October, peaked in August, and cluster in space in southwestern and southeastern lower Michigan. Cases occurred in glacial outwash and ice-contact landscapes in glacial interlobate zones. EEE virus (EEEV) was recovered from Culiseta melanura, Coquillettidia perturbans, five species of Aedes, and other mosquito species near horse and human case sites. Virus isolations or presence of neutralizing antibodies in several passerine species of birds suggest broad EEEV-bird associations. White-tailed deer and other wildlife were also affected. Geographic spread to northern areas of the state suggests expansion of this disease system into new and unsuspected foci.

FOOT INJURIES IN MICHIGAN, USA, GRAY WOLVES (CANIS LUPUS), 1992-2014.

The range of gray wolves (Canis lupus) in the contiguous US is expanding. Research and monitoring to support population recovery and management often involves capture via foothold traps. A population-level epidemiologic assessment of the effect of trap injuries on wolf survival remains needed to inform management. We describe the baseline rate, type, and severity of foot injuries of wolves born 1992-2013 in Michigan's Upper Peninsula, evaluate the reliability of field-scoring trap-related injuries, and the effect of injuries on wolf survival. We assessed foot injuries by physical and radiographic exam at postmortem and/or time of capture for 351 wolves using the International Organization for Standardization 10990-5 standard and the effects of injuries, sex, age, previous capture and body condition on survival using proportional hazards regression. We used ordinal regression to evaluate epidemiologic associations between sex, age, previous capture, body condition, cause of death and injury severity. Most wolves (53%) experienced no physically or radiographically discernable foot injuries over their lifetimes. Among those wolves that did experience injuries, 33% scored as mild. Foot injuries had little epidemiologically discernable effect on survival rates. Wolves with higher foot trauma scores did experience an increased risk of dying, but the magnitude of the increase was modest. Most limb injuries occurred below the carpus or tarsus, and scoring upper-limb injuries added little predictive information to population-level epidemiologic measures of survival and injury severity. There was little association between injury severity and cause of death. Based on necropsy exams, previous trap injuries likely contributed to death in only four wolves (1.1%). Our results suggest that injuries resulting from foothold traps are unlikely to be a limiting factor in recovery and ongoing survival of the Michigan gray wolf population.

Eastern Equine Encephalitis Virus in Visibly Affected Ruffed Grouse (Bonasa umbellus) in Michigan, Minnesota, and Wisconsin, USA.

Eastern equine encephalitis virus (EEEV) infects many avian species but has rarely been described in Ruffed Grouse (Bonasa umbellus). Between September and December 2019, 40 Ruffed Grouse, most in poor physical condition, were submitted to the Michigan, Wisconsin, and Minnesota (US) Departments of Natural Resources; eight were positive for EEEV.

Chronic Wasting Disease Diagnostic Discrepancies: The Importance of Testing Both Medial Retropharyngeal Lymph Nodes.

Chronic wasting disease (CWD) of white-tailed deer (Odocoileus virginianus) is a fatal neurologic disease that is spreading across North America. A common surveillance protocol for CWD currently involves screening with an enzyme-linked immunosorbent assay (ELISA) followed by confirmatory testing with immunohistochemistry (IHC). Medial retropharyngeal lymph nodes (MRPLN) are the tissue of choice to diagnose CWD in free-ranging white-tailed deer. We examined left and right MRPLN from 101 ELISA-positive deer harvested from 2015 to 2019 to determine the prevalence of cases in which prion protein was not detected by IHC as well as differences in IHC labeling between contralateral lymph nodes. Prion protein was not detected using IHC in either MRPLN in 5.9% (6/101) of cases. There was a significant but weak positive relationship between the number of IHC-positive follicles and ELISA optical density values (R2=0.08, P=0.039). Mean optical density values in IHC-positive MRPLN were higher than in IHC-negative MRPLN; however, this was not statistically significant (P=0.260). Failure to confirm ELISA diagnoses with IHC may have been because the methods tested different areas of MRPLN, or that there were differences in test sensitivity or antibody affinity. An additional 5.9% (6/101) of cases had one IHC-positive MRPLN, whereas the contralateral MRPLN was IHC negative. Therefore, testing a single MRPLN for CWD may lead to false-negative results, regardless of methodology, which highlights the importance of collecting and testing both MRPLN.

Lead poisoning from ingestion of fishing gear: A review.

Many publications have investigated the ingestion and toxicity of metallic lead from hunting and the shooting sports. However, there is limited literature on toxicity associated with the ingestion of lead fishing weights, despite our knowledge of damage caused to many species from entanglement in lines, nets, and fish-hooks. This paper surveys current knowledge of species poisoned by ingestion of lead fishing gear and the types of gear that have been implicated. We review the impacts of lead fishing tackle on wildlife species and human health and describe the efficacy of efforts to reduce the use of lead tackle through voluntary, educational, and regulatory approaches to encourage adoption of non-toxic fishing gear. The authors emphasize the need for further research and policy initiatives to deal with this serious problem.

Mortality Due to Toxoplasmosis in Suburban Eastern Fox Squirrels ( Sciurus niger) in Michigan, USA.

Three separate mortality events affecting wild eastern fox squirrels ( Sciurus niger) were investigated in suburban areas within southeastern Michigan, US over a 3-yr period from the summer of 2015 through the winter of 2017. A total of seven squirrels were submitted for investigation. The squirrels were generally in fair to good body condition with moderate fat deposits. The tissues that most commonly exhibited gross or histologic lesions included the lungs, liver, and heart, whereas spleen and brain exhibited lesions less frequently. Lung lesions in all seven squirrels consisted of moderate interstitial pneumonia with necrosis and moderate to high numbers of protozoal organisms. Livers in four out of seven squirrels had multifocal necrosis associated with low to moderate numbers of protozoal organisms. Three out of seven brains examined had mild nonsuppurative meningoencephalitis with widely scattered protozoal cysts. Protozoal organisms observed in various tissues were strongly immunoreactive to Toxoplasma gondii antibody by immunohistochemical staining. Other primary disease conditions tested for included West Nile virus infection, pesticides, and anticoagulants. Toxoplasma gondii can cause disease and mortality in a variety of wild squirrel species, especially near human settlements, and would merit more attention.

PREVALENCE AND DISTRIBUTION OF PSEUDOGYMNOASCUS DESTRUCTANS IN MICHIGAN BATS SUBMITTED FOR RABIES SURVEILLANCE.

Since 2006, bat populations in North America have suffered devastating mortality from an emerging disease known as white-nose syndrome (WNS). The causal agent of WNS is the fungus Pseudogymnoascus destructans. In April 2014, WNS was discovered in little brown bats ( Myotis lucifugus ) in Michigan, US, and has since been documented in 12 counties. Because current surveillance for WNS focuses primarily on mine-hibernating species in winter, it is subject to geographic, species, and seasonal bias. To investigate species affected and potential associations of gender, seasonal life cycle, and region with P. destructans prevalence, 1,040 rabies-negative bats were sampled from May 2014 to May 2015 from animals submitted as part of statewide rabies surveillance. The vast majority (96%) of the sample population consisted of big brown bats ( Eptesicus fuscus ), a noncavernicolous species. Two methods were used to detect P. destructans: fluorescence of the muzzle, wing, and tail membranes under ultraviolet light and PCR targeting genomic DNA on wing samples. Only five bats (0.5%), all M. lucifugus , were confirmed positive after nucleic acid sequencing of PCR amplicons. No other species were infected. All infected bats were collected from April to May, coinciding with their emergence from hibernation. As P. destructans and WNS spread westward, novel surveillance streams may provide a useful tool for wildlife management agencies seeking to detect the fungus where winter hibernacula such as caves and mines are absent or otherwise inaccessible.