Ted H. Noon

Fumonisin B1 Levels Associated with an Epizootic of Equine Leukoencephalomalacia

During the fall of 1989, an episode of equine leukoencephalomalacia involved 18 of 66 purebred Arabian horses at a breeding/training stable in Arizona. Of the 18 horses affected, the condition was fatal in 14. These horses, as well as 48 unaffected horses, had been fed a diet containing a substantial amount of white corn screenings. Gross pathologic findings included liquefactive necrosis in parts of the cerebral white matter and hemorrhagic foci of various sizes in the brain stem. Histopathologic findings included rarefied white matter with pyknotic nuclei and eosinophilic cytoplasm. Thin-layer chromatography, high-performance liquid chromatography, and gas chromatography/mass spectroscopy were utilized to identify and quantitate fumonisin B1 in 3 samples of corn from the farm. Concentrations of fumonisin B1 range from 37 to 122 ppm. Fumonisin B1 was also detected. Using information on diet, animal weights, and feeding practices, estimates of total fumonisin B1 dosage were determined. This is the first definitive report on equine leukoencephalomalacia and associated fumonisin B1 concentrations.

Caprine Herpesvirus-2 in Association with Naturally Occurring Malignant Catarrhal Fever in Captive Sika Deer (Cervus Nippon)

Three female sika deer from a single captive herd were submitted for postmortem examination over a 139-day period. The first 2 deer submitted were reported to have lost body mass for 20 days to 1 month before euthanasia. One of these deer had diarrhea, the other had a crusting dermatitis on the nasal planum and inner aspects of both pinnae. The third hind did not have any signs of disease before it was found seizuring and was immediately euthanatized. Microscopically, all 3 animals had a lymphocytic vasculitis typical of malignant catarrhal fever (MCF), with the most severe lesions in the brain. All 3 deer were polymerase chain reaction (PCR) positive for caprine herpesvirus 2 (CpHV-2) and were negative for ovine herpesvirus 2 (OHV-2). Two healthy goats that were housed adjacent to the deer were also PCR positive for CpHV-2 and PCR negative for OHV-2. The CpHV-2, PCR amplicons from the hinds, and the 2 healthy goats had an identical single base polymorphism. A male sika deer that was housed with the hinds and a fawn from 1 of the hinds remained asymptomatic and were PCR negative for CpHV-2. This represents the first report of mortality with MCF-like lesions in association with CpHV-2.

Neuroaxonal Degeneration in Sheep Grazing Sorghum Pastures

During the fall of 1992, 250 (10%) of 2,500 Rambouilet cross feeder lambs grazing Sorghum bicolor developed neurologic signs including weakness, ataxia, head shaking, knuckling of the fetlocks, inability to rise, and opisthotonos. One hundred fifteen (46%) of the affected lambs died. Twenty of the surviving lambs exhibited residual neurologic signs of ataxia when stressed. At the same time, 275 (25%) of 1,100 ewes grazing a nearby sudex pasture (S. sudanese × S. bicolor) gave birth to lambs that were weak and unable to rise. Newborn lambs exhibited extensor rigidity and opisthotonos when assisted to a standing position. The dystocias that occurred were due to lambs with contracted limbs (arthrogryposis). All affected lambs died or were euthanized. Histologic examination of the brains of 3 feeder lambs and 9 newborn lambs revealed similar microscopic lesions. The predominant change was the presence of focal axonal enlargements (spheroids) in the proximal segments of axons, which were restricted to the nuclei of the medulla, cerebellum, and midbrain. In addition, the spinal cord contained spheroids in the ventral horn gray matter of the 6 newborns examined. Ultrastructurally, the spheroids were composed of aggregates of neurofilaments, mitochondria, vesicular bodies, and dense bodies bounded by a thin myelin sheath. There was mild gliosis in the more severely affected animals of both groups. There was minimal Wallerian degeneration in the white matter adjacent to affected nuclei in the brain and the ventromedial and dorsolateral funiculi of the spinal cord. This is the first detailed report of Sorghum toxicity in sheep.

Infectious Keratoconjunctivitis in Bighorn Sheep, Silver Bell Mountains, Arizona, USA

An infectious keratoconjunctivitis (IKC) epizootic in bighorn sheep (Ovis canadensis) occurred in the Silver Bell Mountains, Arizona, USA, from 1 December 2003 to 31 March 2004. We used standard culture methods and polymerase chain reaction (PCR) amplification of the 16S rRNA gene to test for the causative agents of IKC and other diseases reported to be associated with bighorn sheep populations. All bighorn sheep and domestic goat test results were negative except for Mycoplasma spp. and Branhamella spp. The culture and PCR results differed. Conjunctival swabs from four of 19 IKC-affected bighorn sheep tested by culture were positive for Mycoplasma spp., whereas 22 of 22 bighorn sheep samples tested by PCR were positive for Mycoplasma spp. None of 13 domestic goats tested positive by culture for Mycoplasma spp., whereas five of 16 tested positive by PCR. Three of 16 domestic goats and seven of 24 IKC-affected bighorn sheep tested positive for Branhamella spp. by culture. Bighorn sheep began showing clinical signs of IKC between 21 and 28 days following initial detection of domestic goats in bighorn sheep habitat. The IKC epizootic lasted 122 days, and individual bighorn sheep were blind for an average of 38.4 days. Given the clear potential for disease transmission to bighorn sheep, we recommend that land managers not allow the pasturing of domestic goats near occupied bighorn sheep habitat.

Serologic Survey for Antibodies to Canine Distemper Virus in Collared Peccary (Tayassu tajacu) Populations in Arizona

In 1989, a disease outbreak was observed among collared peccaries (javelina, Tayassu tajacu) in southern Arizona (USA) and canine distemper virus (CDV) was isolated from affected animals. Subsequently, 364 sera were collected from hunter-harvested javelina over a 4 yr period (1993–96) and were tested for antibody to CDV. Neutralizing antibody to CDV was detected in 58% of the serum samples suggesting that CDV infection is probably enzootic in the collared peccary populations of southern Arizona.

Epizootiology of Hemorrhagic Disease in Mule Deer in Central Arizona

We report two male mule deer (Odocoileus hemionus) mortalities that occurred near Prescott, Arizona (USA) in September 2001. Necropsy lesions were compatible with those described for hemorrhagic disease (HD). Bluetongue (BTV) and epizootic hemorrhagic disease (EHDV) viral RNA were identified in tissues from one deer and EHDV viral RNA was identified in the other via reverse transcription-polymerase chain reaction (RT-PCR). Virus isolation attempts were unsuccessful in both cases. To determine geographic range and viral serotypes involved, we collected blood samples from healthy hunter-harvested male mule deer in three game management units near Prescott in October 2001. Forty-one blood samples were collected and antibodies against EHDV and/or BTV were found in 21/41 (51%) samples as determined by agar immunodiffusion. Serum neutralization test results suggest that multiple EHDV and BTV serotypes are present in Arizona.

Hemorrhagic disease in deer in Arizona

Two mule deer (Odocoileus hemionus) and one white-tailed deer (Odocoileus virginianus) in Arizona (USA) were submitted for necropsy. Gross and microscopic lesions compatible with hemorrhagic disease (HD) were observed in all three deer. Epizootic hemorrhagic disease virus type 2 (EHDV-2) was isolated from two of the deer. To our knowledge, this is the first documentation of HD in deer in Arizona. Two of the mortalities were attributed to EHDV-2 infection.

Hemorrhagic disease in bighorn sheep in Arizona

Two bighorn sheep from Arizona (USA) were submitted for necropsy. One was a Rocky Mountain bighorn (Ovis canadensis canadensis) and the other was a desert bighorn (Ovis canadensis mexicana). Both had lesions consistent with those of hemorrhagic disease (HD). Epizootic hemorrhagic disease virus (EHDV) type-2 and bluetongue virus (BTV) type-17, respectively, were isolated from the sheep tissues. To our knowledge, HD caused by either EHDV or BTV infection has not been documented previously in Arizona bighorn sheep.

Hemopericardium in a Dog Due to Hemorrhage Originating in a Heart Base Thymic Remnant

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Population Dynamics and Behavior of Bighorn Sheep with Infectious Keratoconjunctivitis

Abstract Introduced disease is a major mortality factor in some populations of bighorn sheep (Ovis canadensis). Epizootics of infectious keratoconjunctivitis (IKC) and contagious ecthyma occurred in bighorn sheep in the Silver Bell Mountains of south-central Arizona, USA, from 1 December 2003 to 31 March 2004. Our objectives were to 1) investigate the influence of the epizootic on abundance and demographics and 2) examine how IKC affected the mortality, behavior, and movements of clinically affected animals. Morbidity was 39%, and all sex and age classes were affected. The population declined 23%, with most mortality in the adult female (1 M, 11 F) segment of the population. Of the diseased animals that were marked (n = 27), 44% recovered and 44% died. Predation (50%) and starvation (33%) were the primary causes of mortality of diseased bighorn sheep. Bighorn sheep that were infected spent less time feeding and moved less than noninfected animals during the epizootic. Managers might be able to minimize losses of infected animals through predator control. To minimize losses to starvation, managers should refrain from any activity that disturbs infected animals (including treatment) because disturbances increase energy expenditures and expose infected animals to injury.