CAHFS Connection - February 2025

Avian

Highly pathogenic avian influenza (H5 GsGD subtype), infectious laryngotracheitis (ILT), and infectious coryza were diagnosed in a commercial cage-free flock of 104-week-old layer hens. Birds were originally submitted due to increased mortality starting at 17 birds per day in a house of 26,400 birds, which increased to 48 birds the subsequent day. Gross and microscopic lesions included muco-hemorrhagic tracheitis, edematous conjunctivas, airsacculitis, sinusitis, and rhinitis.

Rickets was diagnosed in a flock of 9-day-old commercial Broad Breasted White turkey poults. The birds presented with splaying of the legs at the coxo-femoral joint, rubbery tibias and beaks, dehydration, and empty gizzards. The diagnosis was confirmed by typical histologic lesions of rickets in the sections of tibias. Rickets is rarely seen in commercial poultry and is most commonly associated with errors in the feed mixing.

Bovine

H5N1 Avian influenza (AI) virus was the cause of sudden death in 1- to 4-day-old dairy calves, at several calf ranches. Grossly, the calves had dark red, wet lungs with prominent interlobular septa. Microscopically, there was necrotizing bronchiolitis and lymphocytic vasculitis. H5N1 AI virus was detected by PCR on lung swabs. Airways were positive on Influenza A immunohistochemistry. It is speculated that the affected calves were infected in their respective home dairies.

Bovine herpes virus 1 (BHV-1) encephalitis was diagnosed in an 11-month-old Black Angus heifer that exhibited neurological signs before death. A postmortem examination and additional workup revealed severe necrotizing meningoencephalitis associated with BHV-1. In addition to affecting the respiratory system, BHV-1 has been linked to infection of the reproductive system, conjunctivitis, abortion, encephalomyelitis, and mastitis.

Equine

Right temporohyoid osteoarthropathy in a 22-year-old Quarter horse mare resulted in right-sided facial paralysis, hyperesthesia, muscle fasciculations, abnormal gait, inability to chew, and aggressive behavior. Necropsy revealed a large callus in the proximal stylohyoid joint expanding and effacing the tympanohyoid process, and extending to the petrous bone. Histopathology identified degenerative neuropathy of the right roots of facial and vestibulocochlear nerves, and distal facial nerve

Pigs

Streptococcus suis septicemia was the cause of sudden death in six out of nine 5-week-old pigs that were recently weaned. One pig submitted for necropsy had meningoencephalitis, pleuropneumonia, splenitis, and hepatitis; S. suis was isolated from multiple organs. Tissues from a field necropsy on another piglet revealed congenital heart defects, including ventricular septal defect, valvular dysplasia, and a globose heart.

Mixed viral and parasitic infection resulted in the sudden death of a 4-month-old crossbred gilt. On necropsy, the lungs were diffusely mottled dark red to purple, failed to collapse, and had prominent interlobular septa. The distal trachea contained stable froth. Histology of the lungs had moderate numbers of Metastrongylus in bronchioles mixed with fibrin, mucus, and edema. Porcine reproductive and respiratory virus (PRRS) was detected by PCR in the lung and porcine circovirus-2 was detected in lung, tonsil and lymph node by immunohistochemistry. The pig was also deficient in copper (3.6ppm, normal 5-25ppm) and selenium (0.28ppm, normal 0.4-1.2ppm). Trichuris spp. and Ascaris spp. eggs were detected in feces.

Small Ruminant

Toxoplasmosis was the cause of abortion of two of four submitted fetuses from a goat dairy that had nine, approximately 4-month gestation, abortions, and some retained placentas in first-time yearlings. Toxoplasma gondii zoites were detected by immunohistochemistry in a focal area of placentitis with mineralization in one fetus and in the brain of a second fetus. No placentas, which is often a site affected by Toxoplasma, were available for three fetuses. Two of the four fetuses had very low copper levels of 6.3-6.8 ppm (normal 25-150ppm).