CAHFS Connection - December 2025

Avian

Infectious coryza was diagnosed in a hen and a rooster from the same farm with history of severe respiratory distress. The right side of the face of the hen was swollen. On postmortem examination there was a large mat of fibrin occluding the glottis of the rooster (Fig. 1), and occupying the right infraorbital sinus of the hen. On histopathology the rooster’s glottis and hen’s sinus had fibrino-necrotic material with intralesional colonies of bacteria (Fig. 2). Avibacterium paragallinarum, the cause of infectious coryza, was identified by PCR.

^{Figure 1. A large mat of yellow fibrin occludes the glottis of the rooster (arrow)}

^{Figure 2. On histopathology, the glottis was occluded by a large mat of fibrin (asterisks). The laryngeal epthelium was thickened (thin arrows).}

Proventricular adenocarcinoma was diagnosed in a seven-year-old, female, Budgerigar with history of intermittent lethargy and weight loss. On necropsy, the submitting veterinarian noted an enlarged proventriculus. On histology, a diagnosis of proventricular adenocarcinoma was made. Proventricular adenocarcinoma in budgerigars has been associated with Macrorhabdus ornithogaster (avian gastric yeast) infection, although in the current case, no yeasts with morphology consistent with M. ornithogaster were observed.

Bovine

Q fever was diagnosed in a dystocic premature, stillborn Jersey fetus that had no gross or microscopic lesions. Coxiella burnettii, the agent of Q fever, was identified by PCR in the abomasal fluid of the fetus and the dam’s milk. Q fever is a zoonotic infection which most commonly results in abortions in ruminants. The organism is spread through environmental contamination by placental tissues, urine and feces. Lesions are usually restricted to the placenta, highlighting the importance of submitting placental tissues in all ruminant abortion cases.

Listeria spp. encephalitis was diagnosed in a yearling beef heifer on pasture that was seen circling and progressed to recumbency and paddling. Two days later, the heifer was euthanized. Severe lymphocytic cuffing of blood vessels and scattered suppurative inflammation were observed microscopically in the brain stem. Listeria spp. immunohistochemistry revealed positively-stained intracellular bacteria in the areas with lesions.

Equine

White muscle disease was diagnosed in a 5-6-year-old gelding. The 160 head farm had 15 horses, half under 3.5 years of age, die over four months with similar signs, which included inability to drink, variable limb paralysis, and colic. There were no significant gross findings on necropsy. On microscopic evaluation, all evaluated skeletal and cardiac muscles showed variable degrees of degeneration and necrosis. There was a moderate deficiency of vitamin E and selenium. Clinical signs and microscopic findings, coupled with deficiency of vitamin E and selenium confirmed a diagnosis of white muscle disease. This condition is most commonly seen in foals and young horses, but it can also affect adults. Affected horses often have trouble swallowing, putting them at risk for developing pneumonia and dehydration. Clinical signs include rapid, irregular heartbeat, muscle stiffness and trembling, and difficulty getting up.

Herpesvirus pneumonia and systemic infection was diagnosed in a 14-year-old female donkey with a 5-day history of fever, cough, ocular and nasal discharge and dyspnea prior to death. The animal was shipped across multiple states and kept in an enclosed trailer with a group of other donkeys who also became sick. Equine influenza was previously diagnosed in the herd but had resolved prior to recent presentation. Others in the group tested positive for Equine herpesvirus-1 (EHV-1) and Asinine herpesvirus-3 (AHV-3). On necropsy, all lung lobes were diffusely pale, firm, and over-inflated. There were marked segmental hemorrhages throughout the small intestine and multifocal hemorrhages throughout the mucous membranes and bladder mucosa. On histologic evaluation, the lungs showed a marked interstitial pneumonia with intranuclear eosinophilic viral inclusions, consistent with herpesvirus. Both EHV-1 (neuropathogenic strain) and AHV-3 were confirmed on PCR of the lungs. AHV-3 primarily affects donkeys, while EHV-1 is a pathogen that can infect all equids, including donkeys. Recent studies have shown that EHV-1 can cause respiratory disease, abortion, and death in donkeys, and is a growing concern.

Porcine

Polyserositis was diagnosed in a 6-month-old cross-bred gilt with a history of hemorrhagic diarrhea, vomiting, and inappetence. On necropsy there was severe polyserositis. Renal cysts were identified in the left kidney. Streptococcus suis was isolated from the peritoneum on aerobic culture. Polyserositis is a widespread and important disease associated with economic losses in many pig farms. The most common bacterial causes of polyserositis in pigs include Glaesserella parasuis, Mycoplasma hyorhinis, Streptococcus suis, and Escherichia coli.

Small Ruminants

Neospora caninum was detected in an aborted black-faced crossbred lamb from an ewe that had aborted twins, one fresh and one mummified. On histology, there was mild lymphoplasmacytic myocarditis in one fetus, while immunohistochemistry (IHC) on the placenta showed positive labeling for N. caninum within trophoblasts. Although Neospora caninum is a recognized cause of abortion in cattle, it is rarely reported in small ruminants. Additional testing for Toxoplasma gondii, Coxiella burnetii, Campylobacter spp., and Border disease virus was negative or inconclusive. This case highlights the diagnostic value of IHC in identifying uncommon infectious causes of abortion in sheep.

Coccidioidomycosis and hepatic carcinoma were diagnosed in a 15-year-old, female impala with history of progressive weight loss. Valley Fever (Coccidioides spp.) resulted in pyogranulomatous lesions affecting the lungs, trachea, liver, and lymph nodes (Fig. 3). In addition, the impala had a hepatocellular carcinoma involving a large portion of the liver (Fig. 4).

^{Figure 3: Granulomatous lesions in the liver, characterized by macrophages, lymphocytes, multinucleated giant cells, and fungal spherules consistent with Coccidioides spp. (H&E).}

^{Figure 4: Liver with multifocal nodules that correspond to a hepatocellular carcinoma combined with pyogranulomatous hepatitis.}

Wildlife

An outbreak of avian orthoreovirus (AO) was identified as the cause of death in over 100 crows across four counties in northern California. Necropsies and histopathology on four crows revealed moderate splenomegaly and fibrinonecrotizing enteritis in all 4 birds. Avian orthoreovirus (AO) was detected in the small intestine by PCR, and Reoviridae viral particles were observed by direct electron microscopy. Paraclostridium sordellii and Clostridium perfringens were also isolated from two birds, which were considered secondary invaders. AO infection in crows causes high mortality and die-offs, with birds showing minimal clinical signs before death. It has been referred to as “winter mortality of crows”.