Richard W. Gerhold

Frequent Cross-Species Transmission of Parvoviruses among Diverse Carnivore Hosts

ABSTRACT Although parvoviruses are commonly described in domestic carnivores, little is known about their biodiversity in nondomestic species. A phylogenetic analysis of VP2 gene sequences from puma, coyote, gray wolf, bobcat, raccoon, and striped skunk revealed two major groups related to either feline panleukopenia virus (“FPV-like”) or canine parvovirus (“CPV-like”). Cross-species transmission was commonplace, with multiple introductions into each host species but, with the exception of raccoons, relatively little evidence for onward transmission in nondomestic species.

Molecular characterization of the Trichomonas gallinae morphologic complex in the United States

Abstract Forty-two Trichomonas gallinae isolates were molecularly characterized to determine whether isolates differed in genetic sequence of multiple gene targets depending on host species or geographical location. The 5.8S ribosomal RNA (rRNA) and flanking internal transcribed spacer (ITS) gene regions were amplified by polymerase chain reaction, and the sequences were analyzed phylogenetically. The results of the sequence analysis strongly suggest at least 2 species may exist within the T. gallinae morphologic complex. Based on ITS sequences, one group demonstrated high nucleotide identity to the 3 T. gallinae sequences available in GenBank, whereas the second group was more closely related to T. vaginalis (98%) than to T. gallinae (92%). Two common ground-dove (Columbina passerina) isolates shared a 95% identity with T. vaginalis and a 92% identity with T. gallinae and T. tenax. Sequence analysis of both the 18S rRNA and α-tubulin genes from a subset of the isolates supports the 5.8S-ITS sequence results. All of the T. vaginalis-like isolates originated from Arizona, California, or Texas, whereas T. gallinae isolates were found in all sampled states. Both T. vaginalis-like and T. gallinae isolates were involved in trichomoniasis outbreaks in California and Arizona.

AVIAN VACUOLAR MYELINOPATHY OUTBREAKS AT A SOUTHEASTERN RESERVOIR

Avian vacuolar myelinopathy (AVM) is a neurologic disease of unknown etiology that affects bald eagles (Haliaeetus leucocephalus), American coots (Fulica americana), and several species of waterfowl. An unidentified neurotoxin is suspected as the cause of AVM, which has been documented at several reservoirs in the southeastern United States. We conducted diagnostic and epidemiologic studies annually during October–March from 1998–2004 at Clarks Hill/Strom Thurmond Lake on the Georgia/South Carolina border to better understand the disease. Avian vacuolar myelinopathy was confirmed or suspected as the cause of morbidity and mortality of 28 bald eagles, 16 Canada geese (Branta canadensis), six American coots, two great-horned owls (Bubo virginianus), and one killdeer (Charadrius vociferus). Active surveillance during the outbreaks yielded annual average prevalence of vacuolar lesions in 17–94% of coots, but not in 10 beavers (Castor canadensis), four raccoons (Procyon lotor), and one gray fox (Urocyon cinereoargenteus) collected for the study. Brain lesions were not apparent in 30 Canada geese collected and examined in June 2002. The outbreaks at this location from 1998–2004 represent the most significant AVM-related bald eagle mortality since the Arkansas epornitics of 1994–95 and 1996–97, as well as the first confirmation of the disease in members of Strigiformes and Charadriiformes.

Sarcocystis neurona-associated Meningoencephalitis and Description of Intramuscular Sarcocysts in a Fisher (Martes pennanti)

A free-ranging juvenile fisher (Martes pennanti) with ataxia, lethargy, stupor, and intermittent, whole-body tremors was examined postmortem. Microscopically, the fisher had protozoal meningoencephalitis caused by Sarcocystis neurona, which was confirmed by immunohistochemistry, polymerase chain reaction (PCR) and restriction fragment length polymorphism testing, and genetic sequencing. Sarcocysts found in the skeletal muscle of the fisher were negative for S. neurona by PCR, but were morphologically similar to previous light and electron microscopy descriptions of S. neurona. This is the first report of clinical neural S. neurona infection in a fisher.

Molecular Characterization of Histomonas meleagridis and Other Parabasalids in the United States Using the 5.8S, ITS-1, and ITS-2 rRNA Regions

abstract:  Extracted DNA from 28 Histomonas meleagridis-infected avian tissue samples from multiple hosts and geographic locations was analyzed for variation in the 5.8S rRNA and the flanking internal transcribed spacer regions (ITS 1 and ITS 2). Samples were amplified by polymerase chain reaction, sequenced, and compared with known sequences from GenBank accessions of H. meleagridis and other related protozoa. The analyses revealed significant genetic variation within H. meleagridis sequences and suggested the possibility of multiple genotypes within the samples or a possible misdiagnosis. Related protozoa found in some samples were mostly identified as Tetratrichomonas spp. However, 1 sample had a 93% identity to Simplicimonas similis, a newly described organism, suggesting the possibility of a new pathogen in poultry. A phylogenetic tree analyzing the 5.8S and flanking ITS regions was inconclusive and we were unable to resolve all H. meleagridis into a single grouping. In contrast, a tree constructed only on the 5.8S rRNA grouped all but 1 H. meleagridis sample into 1 clade, including GenBank accessions submitted from Europe. This suggests that the 5.8S region alone is more reliable in identifying H. meleagridis than are the combined 5.8S and flanking ITS regions. There was no correlation between genotypes and host species or geographic location, suggesting that H. meleagridis moves freely between multiple avian species in the sampled regions.

Mercury Poisoning in a Free-Living Northern River Otter (Lontra canadensis)

A moribund 5-year-old female northern river otter (Lontra canadensis) was found on the bank of a river known to be extensively contaminated with mercury. It exhibited severe ataxia and scleral injection, made no attempt to flee, and died shortly thereafter of drowning. Tissue mercury levels were among the highest ever reported for a free-living terrestrial mammal: kidney, 353 μg/g; liver, 221 μg/g; muscle, 121 μg/g; brain (three replicates from cerebellum), 142, 151, 151 μg/g (all dry weights); and fur, 183 ug/g (fresh weight). Histopathologic findings including severe, diffuse, chronic glomerulosclerosis and moderate interstitial fibrosis were the presumptive cause of clinical signs and death. This is one of a few reports to document the death of a free-living mammal from presumed mercury poisoning.

Trichomonas stableri n. sp., an agent of trichomonosis in Pacific Coast band-tailed pigeons (Patagioenas fasciata monilis)

Graphical abstract

Johne's Disease in a Free-Ranging White-tailed Deer from Virginia and Subsequent Surveillance for Mycobacterium avium subspecies paratuberculosis

Johnes disease (paratuberculosis) was diagnosed in a 2-yr-old, male, free-ranging white-tailed deer (Odocoileus virginianus) from Fauquier County, Virginia, USA, based on histopathology and culture for Mycobacterium avium subspecies paratuberculosis. Clinical and pathologic findings included emaciation; loss of body fat; chronic diarrhea; severe, chronic, diffuse granulomatous colitis with intrahistiocytic acid-fast bacilli; moderate, chronic granulomatous lymphadenitis with intrahistiocytic acid-fast bacilli; as well as moderate chronic, multifocal, lymphoplasmacytic hepatitis. These findings are consistent with previous reports of Johnes disease in cervids. Subsequent targeted surveillance of 10 emaciated deer with diarrhea, as well as sampling of 72 asymptomatic deer for M. avium subsp. paratuberculosis using culture of multiple tissue types, as well as serology using an enzyme-linked immunosorbent assay (ELISA) optimized for cervid antibody detection, did not reveal any additional cases of infection in this geographic region. To date, this appears to be an isolated case of Johnes disease in a free-ranging white-tailed deer, and infection with the causative agent for Johnes disease appears to be an infrequent occurrence in deer from this region. The origin of infection was most likely domestic ruminants. This is the first report of clinical Johnes disease in a free-ranging white-tailed deer outside of the Florida Keys, USA. Stressors, such as high deer population density and low selenium levels, may have contributed to the development of clinical disease in this case and warrant further investigation.

Necropsy Findings and Arbovirus Surveillance in Mourning Doves from the Southeastern United States

Mourning doves (Zenaida macroura) are the most abundant and widespread native member of the columbid family, as well as a major migratory game species, in the United States. However, there is little information on mortality factors in mourning doves. Records of necropsy accessions at the Southeastern Cooperative Wildlife Disease Study (SCWDS) from 15 southeastern states, from 1971 through 2005, were reviewed. One hundred thirty-five mourning doves were submitted from nine states during the 35-yr period. Trichomonosis constituted 40% (n=54) of all diagnoses and was the most frequent diagnosis. Toxicoses and avian pox constituted 18.5% (n=25) and 14.8% (n=20) of all diagnoses, respectively. Remaining diagnoses included trauma, suspected toxicosis, Ascaridia columbae infection, suspected tick paralysis, and undetermined. Adults were observed more frequently with trichomonosis (94.1%) and toxicoses (68%) as compared to juveniles, but a gender predisposition was not apparent for either disease. Age and gender predilections were not apparent for cases of avian pox. The majority of the trichomonosis and avian pox cases were observed in the spring-summer, whereas the majority of the toxicosis cases were observed in the winter-spring. Additionally, the Georgia Department of Human Resources–Division of Public Health and West Virginia Department of Health and Human Resources submitted 809 mourning doves to SCWDS from 2001 through 2005 for West Nile virus surveillance efforts. West Nile virus was isolated from 2.1% (n=17) and eastern equine encephalitis virus (EEEV) was isolated from 0.2% (n=2) of the submitted birds.

Diagnosis of Parelaphostrongylus spp. infection as a cause of meningomyelitis in calves

Migration of Parelaphostrongylus spp. has been documented to cause central nervous system damage in a number of aberrant host species but appears to be uncommon in cattle. The current report describes the clinical and laboratory findings, antemortem and definitive diagnosis, and response to treatment of Parelaphostrongylus spp. infection in five 3–7- month-old Limousin calves from 2 farms. All calves had signs of acute (n = 2) and chronic (n = 3) progressive spinal cord dysfunction. Cerebrospinal fluid analysis revealed a marked eosinophilic (acute cases) or lymphocytic (chronic cases) pleocytosis and elevated protein in all calves. A necropsy and histopathologic evaluation was performed on 2 euthanized calves, and histopathology revealed lymphoplasmacytic and eosinophilic meningomyelitis with multiple intradural and intramedullary expansile hyperplastic lymphoid nodules containing germinal centers and nematode fragments. DNA sequencing was performed on nested polymerase chain reaction products amplified with parasite-specific primers obtained from formalin-fixed and frozen spinal cord; PCR products from these 2 calves were 100% identical to Parelaphostrongylus species on DNA sequencing, confirming the diagnosis. Surviving calves rapidly improved following treatment with anthelmintics and corticosteroids. This case series identified Parelaphostrongylus spp. (likely P. tenuis) as a cause of spinal cord disease in calves and highlights the need for vigilance against aberrant parasite migration in calves grazing wet, snail-infested pastures. Cerebrospinal fluid eosinophilia is useful for supporting an antemortem diagnosis of Parelaphostrongylus in calves with acute neurologic disease; however, a lymphocytosis is observed in chronic or treated cases.