Multiple genotypes of highly pathogenic avian influenza (HPAI) H5 clade 2.3.4.4b viruses have caused epizootics in wild birds and poultry. The HPAI H5N1 genotype C virus caused a modest epizootic, whereas the occurrence of the HPAI H5N1 genotype AB virus in 2021 resulted in the largest avian influenza epizootic in Europe to date. Here we studied the pathogenicity of two HPAI H5N1 viruses by experimentally infecting chickens, Pekin ducks, Eurasian wigeons and Barnacle geese. Our study demonstrates that pathogenicity of the H5N1-2021-AB virus is lower in Pekin ducks, Eurasian wigeons and Barnacle geese compared to the H5N1-2020-C virus, whereas virus shedding was high for both viruses. After inoculation with H5N1-2021-C viral antigen expression was higher in the brain of Pekin ducks, Eurasian wigeons and Barnacle geese, which caused higher mortality compared to inoculation with H5N1-2021-AB virus. Subclinical infections occurred in Pekin ducks and Eurasian wigeons and mortality was reduced in Barnacle geese after inoculation with H5N1-2021-AB virus while H5N1-2020-C virus caused high morbidity and mortality in these species. This H5N1-2021-AB virus trait may have contributed to efficient spread of the virus in wild bird populations. Therefore, high mortality, virus shedding and long-lasting viral antigen expression found in Barnacle geese may have increased the risk for introduction into poultry.

Usutu virus (USUV) is a zoonotic neurotropic arbovirus related to the West Nile virus that causes mortality in birds and sporadic neurologic human disease. Current research on natural USUV-associated disease lacks data on ocular involvement. This study investigated ocular and periocular tissue involvement in natural USUV infections and associated disease in Eurasian blackbirds ( Turdus merula ). Twenty-two found-dead Eurasian blackbirds were examined. USUV reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) detected 12/22 infected blackbirds. Histology and immunohistochemistry for virus antigen, inflammation (anti-CD3 for T-lymphocytes), and apoptosis (anti-cleaved caspase-3 (CC3)) assessed the virus tropism and associated damage. In the eye of USUV-infected blackbirds, choroiditis was the main finding (9/12), while the pecten oculi (4/12) and optic nerves (4/12) were occasionally affected. Virus antigen was detected in the lesions. The cornea and retina lacked virus antigens and lesions. Periocular soft tissues (12/12) and eyelids (9/12) were also affected. Lesions in the choroid ( P < .001), ciliary bodies ( P < .01), and sclera ( P < .05) were significantly associated with USUV infection. In the choroid, CD3 and CC3 strongly correlated with the virus antigen scores ( P < .0001), suggesting a T-cell response and apoptosis involvement in the ocular damage. A negative correlation was identified for the virus antigen score in choroid and eyelids with USUV RT-qPCR Ct values ( P < .05). This study reports for USUV features consistent with ocular and periocular tropism and disease with a major involvement of the choroid, suggesting a primary ocular vascular spread.

Objectives Given the limited ocular pathology data for common cuttlefish Sepia officinalis and hummingbird bobtail squid Euprymna berryi despite their high visual dependency, the purpose of this study was to investigate and describe the ophthalmic lesions in a cohort of laboratory-housed common cuttlefish and hummingbird bobtail squid. Methods Cases were retrospectively selected from the International Zoo Veterinary Group Pathology database that reported confirmed clinical ophthalmic lesions or histopathological lesions. Twenty-five cases were identified that included clinical records and gross and histopathological examination of whole specimens. The cases included 19 common cuttlefish and six hummingbird bobtail squid, thus providing a sample of 50 eyes and orbital cavities. Results Thirty-two of 50 individual eyes (64%) and 30 of 50 white bodies (60%) were affected. The most frequent lesion that was observed was inflammation (n = 29/32, 91%), primarily manifesting as uveitis (n = 23/32, 72%) and phakitis (n = 10/32, 31%). Cataracts were also common (n = 14/32, 44%), often with cataract-associated inflammation (n = 9/14, 64%). Leukopoietic hyperplasia of the white body was bilaterally observed in 15 of 25 animals (60%) and was thought to be associated with exophthalmos. In the absence of notable intraocular or infraorbital lesions in some animals, this change was considered reactive, likely in response to nonocular lesions, such as ulcerative dermatitis and branchitis. Notable additional findings included hypopyon-like lesions (n = 3/32, 9%), a single case of congenital ocular malformation, and one case with mesenchymal proliferations that were reminiscent of florid fibroplasia. Conclusions This study contributes to the expanding knowledge of cephalopod ocular pathology, with previously unreported findings in these cephalopods including congenital ocular malformation and cases of ­hypopyon-like lesions with proteinaceous material exudation and hemocytes in the anterior chamber. Additionally, it offers specific insights into the ocular pathology of the hummingbird bobtail squid.

A 6‐year‐old female Friesian horse was admitted with pyrexia, dullness, weight loss, watery faeces and mild bilateral mucoid nasal discharge. Radiographic and ultrasonographic examination of the thorax indicated a large mid‐thoracic soft tissue mass, and the horse was euthanased because of a poor prognosis. At postmortem examination, it was found that the lung tissue was partly replaced by multiple to coalescing soft tissue lesions with a yellow gelatinous aspect, varying in size up to 15 × 15 × 20 cm. Histologically, the mass showed mild pyogranulomatous inflammation associated with large numbers of globular encapsulated 10–20 μm yeasts with or without narrow‐based budding, consistent with multiple coalescing cryptococcomas. Quantitative PCR testing of formalin‐fixed paraffin‐embedded tissue led to the identification of Cryptococcus gattii species complex. To the authors’ knowledge, this is the first case reported in the Netherlands of pulmonary cryptococcomas due to C. gattii sensu lato in a horse that had never travelled abroad.

This case describes a fibrosarcoma on the left upper leg of an adult female rhesus macaque. The patient was initially presented with a defined swelling at the caudolateral side of the upper leg. Medially from the growth, a swollen circular wound had formed with a fistula leading in the direction of the mass. The swelling was firm on palpation and was located in the subcutis, attached to the skin and underlying tissues. No other clinical abnormalities were observed. Treatment was initiated for an abscess with concurrent infection. Unfortunately, despite intensive wound debridement, wound lavage and antibiotic treatment, the growth did not resolve, and the animal was euthanased humanely due to clinical deterioration. Postmortem examination revealed a uniform, firm, white structure that had infiltrated deep into the underlying tissues. Histologically, the mass consisted of pleiomorphic spindle cells in fascicles with a collagenous stroma and negative desmin immunostaining, suggesting diagnosis of a fibrosarcoma.