Hepatogenous photosensitization by Brachiaria spp. in sheep: first report in Mexico

Ruminants are highly susceptible to photosensitization caused by the ingestion of hepatotoxic plants. In two adjacent farms in Colima, Mexico, several sheep exhibited signs of depression and crusting dermatitis involving the ears, periorbital skin, eyelids, nostrils, and axillary regions. Results of serum biochemistry were indicative of liver injury. Post mortem examination revealed jaundice, craniofacial edema as well as an enlarged liver having an orange-brown discoloration; on the cut surface, the hepatic parenchyma had a subtle zonal pattern. Histopathological findings were those of severe necrotizing dermatitis, lymphoplasmacytic cholangiohepatitis, and renal tubular necrosis. Acicular crystals were microscopically and ultrastructurally evident in hepatocytes, Kupffer cells, biliary ducts, renal tubules and interstitium. The clinical, gross and microscopic findings were consistent with hepatogenous photosensitization. A field investigation revealed that affected sheep had been grazing Brachiaria spp., a potentially toxic grass originated from Africa and commonly cultivated in Australia and South America. This grass contains hepatotoxic saponins that cause liver injury and secondary hepatogenous photosensitization. Although frequently reported in South America, to our knowledge, this is the first report of Brachiaria spp. toxicity in Mexico.

Hepatogenous photosensitization by Brachiaria spp. in sheep: first report in Mexico

Ruminants are highly susceptible to photosensitization caused by the ingestion of hepatotoxic plants. In two adjacent farms in Colima, Mexico, several sheep exhibited signs of depression and crusting dermatitis involving the ears, periorbital skin, eyelids, nostrils, and axillary regions. Results of serum biochemistry were indicative of liver injury. Post mortem examination revealed jaundice, craniofacial edema as well as an enlarged liver having an orange-brown discoloration; on the cut surface, the hepatic parenchyma had a subtle zonal pattern. Histopathological findings were those of severe necrotizing dermatitis, lymphoplasmacytic cholangiohepatitis, and renal tubular necrosis. Acicular crystals were microscopically and ultrastructurally evident in hepatocytes, Kupffer cells, biliary ducts, renal tubules and interstitium. The clinical, gross and microscopic findings were consistent with hepatogenous photosensitization. A field investigation revealed that affected sheep had been grazing Brachiaria spp., a potentially toxic grass originated from Africa and commonly cultivated in Australia and South America. This grass contains hepatotoxic saponins that cause liver injury and secondary hepatogenous photosensitization. Although frequently reported in South America, to our knowledge, this is the first report of Brachiaria spp. toxicity in Mexico.(AU)

Bluetongue in white-tailed deer (Odocoileus virginianus) in Northeastern Mexico

Bluetongue (BT) and epizootic hemorrhagic disease of deer (EHD) are two distinct viral hemorrhagic diseases of domestic and wildruminants caused by members of the family Reoviridae and transmitted by Culicoides midges. These conditions have been recognized in Canada and the United States for many years, but not in Mexico. Although in Mexico there is serologic evidence of EHD virus (EHDV) and bluetongue virus (BTV) in domestic and wild ruminants, to our knowledge, there have never been reports of clinical illness or fatalities attributed to either of these viruses. Two free ranging white-tailed deer (Odocoileus virginianus) in twolicensed hunting ranches in Northern Mexico near the Texas border died unexpectedly. Postmortem and microscopic examinations revealed hemorrhagic lesions compatible with viral hemorrhagic disease (Reoviridae: Orbivirus). Tissues from one animal tested positive by RT-PCR for BTV but negative for EHDV. To our knowledge, this is the first time in Mexico where deer dying with hemorrhagic lesions consistent with Bluetongue tested positive for BTV by PCR.(AU)

Bluetongue in white-tailed deer (Odocoileus virginianus) in Northeastern Mexico

Bluetongue (BT) and epizootic hemorrhagic disease of deer (EHD) are two distinct viral hemorrhagic diseases of domestic and wildruminants caused by members of the family Reoviridae and transmitted by Culicoides midges. These conditions have been recognized in Canada and the United States for many years, but not in Mexico. Although in Mexico there is serologic evidence of EHD virus (EHDV) and bluetongue virus (BTV) in domestic and wild ruminants, to our knowledge, there have never been reports of clinical illness or fatalities attributed to either of these viruses. Two free ranging white-tailed deer (Odocoileus virginianus) in twolicensed hunting ranches in Northern Mexico near the Texas border died unexpectedly. Postmortem and microscopic examinations revealed hemorrhagic lesions compatible with viral hemorrhagic disease (Reoviridae: Orbivirus). Tissues from one animal tested positive by RT-PCR for BTV but negative for EHDV. To our knowledge, this is the first time in Mexico where deer dying with hemorrhagic lesions consistent with Bluetongue tested positive for BTV by PCR.

Congenital biliary atresia in a Beefmaster calf

Biliary atresia is a congenital cholangiopathy characterized by a progressive fibrosis of the bile ducts leading to impaired biliary flow, hepatic failure, icterus and early death. This paper describes the gross and microscopic findings in a 4-week-old Beefmaster calf that unexpectedly died with severe jaundice. On postmortem examination, the liver was firm in texture and exhibited an orange-yellow discoloration. Microscopically, there were cholestasis, hyperplasia, fibrosis and obliteration of the bile ducts, and mural fibrosis of the gall-bladder. Massons trichrome and Gomoris stain revealed excessive collagen deposition in the portal areas and biliary ducts, and occasionally around central veins. Immunohistochemistry confirmed biliary epithelial cells, not only lining the bile ducts but also were forming tubular-like structures devoid of a lumen. Blood test was negative for babesiosis and anaplasmosis. Based on these findings, the final diagnosis was congenital biliary atresia.

Congenital biliary atresia in a Beefmaster calf

Biliary atresia is a congenital cholangiopathy characterized by a progressive fibrosis of the bile ducts leading to impaired biliary flow, hepatic failure, icterus and early death. This paper describes the gross and microscopic findings in a 4-week-old Beefmaster calf that unexpectedly died with severe jaundice. On postmortem examination, the liver was firm in texture and exhibited an orange-yellow discoloration. Microscopically, there were cholestasis, hyperplasia, fibrosis and obliteration of the bile ducts, and mural fibrosis of the gall-bladder. Massons trichrome and Gomoris stain revealed excessive collagen deposition in the portal areas and biliary ducts, and occasionally around central veins. Immunohistochemistry confirmed biliary epithelial cells, not only lining the bile ducts but also were forming tubular-like structures devoid of a lumen. Blood test was negative for babesiosis and anaplasmosis. Based on these findings, the final diagnosis was congenital biliary atresia.(AU)

Cardiac rhabdomyoma in a slaughtered heifer

During routine inspection of a slaughtered heifer from a feedlot, the veterinarian in charge condemned the heartdue to a lesion on the endocardium. Histopathology and immunohistochemistry showed that the lesion was composed bycardiac tissues at different degree of differentiation, disordered and out of proportion. The most conspicuous was adispersed population of large, vacuolated and PAS positive cells, enmeshed in excessive fibrous connective tissue. Thesecells, identified as spider cells, resulted markedly positive for desmin, and negative for vimentin, smooth muscle α-actin andmyogenin factor 4. An extensive infiltration by fibro-fatty tissue was other abnormal component of the lesion. Furthermore,abnormal cardiomyoblasts forming tortuous bundles were also recognized. Nonetheless, these cells showed distinctivestriations and even intercalated discs. Some of this abnormal cardiac myoblasts resulted markedly positive for desmin andisolated strands also were positive for smooth muscle α-actin, but negative for myogenin factor 4 and vimentin. Based onthe pathognomonic spider cells and immunoreactivity, the lesion was classified as a cardiac rhabdomyoma. For some, thecardiac rhabdomyomas are not true neoplasms but congenital hamartomas in heart. However, principal component incardiac hamartomas in animals is an abnormal vascular pattern completely different from the lesion herein presented. Basedon the diverse tissue components, their immature and distorted image and, positive results for immunomarkers of earlymyoblast differentiation as well as terminal cardiomyocyte characteristics, dysplasia must be considered as the commondenominator in development of cardiac rhabdomyomas with tissue heterogeneity.(AU)

Cardiac rhabdomyoma in a slaughtered heifer

During routine inspection of a slaughtered heifer from a feedlot, the veterinarian in charge condemned the heartdue to a lesion on the endocardium. Histopathology and immunohistochemistry showed that the lesion was composed bycardiac tissues at different degree of differentiation, disordered and out of proportion. The most conspicuous was adispersed population of large, vacuolated and PAS positive cells, enmeshed in excessive fibrous connective tissue. Thesecells, identified as spider cells, resulted markedly positive for desmin, and negative for vimentin, smooth muscle α-actin andmyogenin factor 4. An extensive infiltration by fibro-fatty tissue was other abnormal component of the lesion. Furthermore,abnormal cardiomyoblasts forming tortuous bundles were also recognized. Nonetheless, these cells showed distinctivestriations and even intercalated discs. Some of this abnormal cardiac myoblasts resulted markedly positive for desmin andisolated strands also were positive for smooth muscle α-actin, but negative for myogenin factor 4 and vimentin. Based onthe pathognomonic spider cells and immunoreactivity, the lesion was classified as a cardiac rhabdomyoma. For some, thecardiac rhabdomyomas are not true neoplasms but congenital hamartomas in heart. However, principal component incardiac hamartomas in animals is an abnormal vascular pattern completely different from the lesion herein presented. Basedon the diverse tissue components, their immature and distorted image and, positive results for immunomarkers of earlymyoblast differentiation as well as terminal cardiomyocyte characteristics, dysplasia must be considered as the commondenominator in development of cardiac rhabdomyomas with tissue heterogeneity.