Postmortem examination (2016-2017) of weanling and older horses for the presence of select species of endoparasites: Gasterophilus spp., Anoplocephala spp. and Strongylus spp. in specific anatomical sites.

Parasite infections are more quantifiable postmortem than antemortem in horses. Thus a study was carried out examining dead horses for specific parasite species. Most of the weanling and older horses submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) for postmortem examination between November 22, 2016 and March 23, 2017 were examined for certain species of internal parasites. The stomach and duodenum from 69 horses were examined for bots (Gasterophilus spp.). Combined data for both Thoroughbred and non-Thoroughbred (16 other than Thoroughbred breeds/mixed breeds) horses revealed that the prevalence of Gasterophilus intestinalis was 19% (n=12) with 2nd instars (x̄ 8.5) and 39% (n=27) with 3rd instars (x̄ 90). The prevalence of Gasterophilus nasalis was 1.5% (n=1) for 2nd instars (x̄ 1) and 7% (n=5) for 3rd instars (x̄ 25). A few third instar G. intestinalis placed in 10% formalin showed slight movement at over two hundred hours later. The cecum and about 25cm of the terminal part of the ileum were examined from 139 horses for tapeworms (Anoplocephala spp.) and large strongyles (Strongylus spp.). The prevalence of A. perfoliata was 44% (n=62) and the average number of specimens per infected horse was 92.5. Strongylus vulgaris and Strongylus edentatus were not found in the gut of any horse.

Prevalence of latent, neuropathogenic equine herpesvirus-1 in the Thoroughbred broodmare population of central Kentucky.

REASON FOR PERFORMING STUDY: An emerging problem of equine herpesvirus-1 (EHV-1) infection in horses in the USA is a high-mortality myeloencephalopathy that commonly occurs where large numbers of horses are stabled. EHV-1 isolates recovered from recent neurological outbreaks represent a mutant virus strain that possesses enhanced neuropathogenicity. A central question of EHV-1 myeloencephalopathy is the latency carriage rate for these mutants of EHV-1 in USA horse populations. OBJECTIVE: To estimate the prevalence of neuropathogenic strains of EHV-1 as latent infections in the Thoroughbred broodmare population of central Kentucky. METHODS: Submandibular lymph nodes (SMLN) were collected during post mortem examination of 132 Thoroughbred broodmares. Total DNA purified from SMLN tissue was tested for the presence of latent EHV-1 DNA by an ultrasensitive magnetic bead-based, sequence-capture, nested PCR method. Differentiation of active from latent infections by EHV-1 was achieved by detection of transcripts of EHV-1 glycoprotein B by reverse transcription PCR. RESULTS: Latent EHV-1 DNA was detected in the SMLN tissues of 71 (54%) of the 132 mares submitted for necropsy. Thirteen (18%) of the 71 latently infected horses harboured the neuropathogenic biovar of EHV-1. Of the 13 horses latently infected with an ORF30 mutant strain of EHV-1, 11 also carried a latent, wild-type strain of the virus in their SMLN tissues. CONCLUSIONS: Neuropathogenic strains of EHV-1 have established a significant presence in the Thoroughbred broodmare population of central Kentucky as latently infected carrier horses. The data also indicate that a highly sensitive DNA detection method is required to identify many instances of EHV-1 latency. POTENTIAL RELEVANCE: The presence of a relatively large biological reservoir of latent, neuropathogenic EHV-1 has the potential for posing emerging equine health and economic threats to the future prosperity of the USA horse industry.

Equine multinodular pulmonary fibrosis: a newly recognized herpesvirus-associated fibrotic lung disease.

Pulmonary fibrosis and interstitial lung disease are poorly understood in horses; the causes of such conditions are rarely identified. Equine herpesvirus 5 (EHV-5) is a gamma-herpesvirus of horses that has not been associated with disease in horses. Pathologic and virologic findings from 24 horses with progressive nodular fibrotic lung disease associated with EHV-5 infection are described and compared with 23 age-matched control animals. Gross lesions consisted of multiple nodules of fibrosis throughout the lungs. Histologically, there was marked interstitial fibrosis, often with preservation of an "alveolar-like" architecture, lined by cuboidal epithelial cells. The airways contained primarily neutrophils and macrophages. Rare macrophages contained large eosinophilic intranuclear viral inclusion bodies; similar inclusion bodies were also found cytologically. The inclusions were identified as herpesviral-like particles by transmission electron microscopy in a single horse. In situ hybridization was used to detect EHV-5 nucleic acids within occasional macrophage nuclei. With polymerase chain reaction (PCR), the herpesviral DNA polymerase gene was detected in 19/24 (79.2%) of affected horses and 2/23 (8.7%) of the control horses. Virus genera-specific PCR was used to detect EHV-5 in all of the affected horses and none of the control horses. EHV-2 was detected in 8/24 (33.3%) of affected horses and 1/9 (11.1%) of the control horses. This disease has not been reported before, and the authors propose that based upon the characteristic gross and histologic findings, the disease be known as equine multinodular pulmonary fibrosis. Further, we propose that this newly described disease develops in association with infection by the equine gamma-herpesvirus, EHV-5.

Three equine cases of mixed hepatoblastoma with teratoid features.

Hepatoblastoma was diagnosed in 3 Thoroughbreds at the University of Kentucky Livestock Disease Diagnostic Center (LDDC) since 1997. Case #1 involved a fetus with a well-demarcated, multilobulated, solitary mass that extended from the left liver lobe. Case #2 was observed in a neonate with a primary hepatic mass and multiple metastases in the skin, brain, meninges, and stylohyoid bone. Case #3 was a solitary hepatic mass incidentally discovered in a neonate at necropsy. Microscopically, the masses were similarly composed of sheets and cords of fetal and embryonal epithelial cells that frequently formed sinusoid-like structures. Intermixed with the neoplastic epithelial cells were variable amounts of hemorrhage, necrosis, osteoid, and bone. Immunohistochemically, the epithelial cells stained variably positive for alpha- fetoprotein, frequently positive for vimentin, and occasionally positive for cytokeratin. All 3 cases were diagnosed as mixed hepatoblastoma with teratoid features.

The effect of 6-aminonicotinamide on testicular development in the rat.

6-Aminonicotinamide (6-AN), a niacin antagonist, was administered sc to pregnant female (1.0, 3.0, or 6.0 mg 6-AN/kg body weight) and neonatal male (1.5, 3.0, 6.0 or 12.0 mg 6-AN/kg body weight) Sprague-Dawley rats on the 15th, 17th and 19th days of gestation or the 5th, 7th and 9th days of life, respectively, to determine the effects of the antimetabolite on testicular morphology and development. In prenatal males, microscopic alterations were present in testes of fetuses from females treated with 6.0 mg 6-AN/kg and consisted of necrosis and loss of gonocytes, and vacuolation of interstitial cells. Histologic changes in testes of neonatal rats treated with 3.0, 6.0 or 12.0 mg 6-AN/kg were qualitatively similar with necrosis and loss of spermatogonia and supporting cells, and increased cross-sectional areas of affected tubules. Quantitation of the number of nuclei/cm2 of seminiferous tubule indicated 6-AN caused a significant reduction in the numbers of supporting cells and spermatogonia/tubular cross-section.

Studies of the teratogenicity of xanthomegnin and viridicatumtoxin in ICR mice.

The myotoxins xanthomegnin and viridicatumtoxin were not teratogenic when administered orally to pregnant ICR mice during the 8-12th and 8-13th days of gestation, respectively. Viridicatumtoxin produced high mortality in mice given 200, 250 or 350 mg/kg of body weight.