Dairy herd size of 190 Friesian, Jersey and Cross bred on South Coast of NSW.
History of Pestivirus and Theileriosis on property.
Vaccinated with 'Pestigard' BVDV vaccine 13/1/10.
Four abortions since. 2 at about 30wks gestation, 2 at about 20wks gestation. Cows showed only slight drop in production prior to aborting. Cow #2890 had been treated with Oxytetracycline 16th & 17th Jan for being 'off', aborted 20/1 (necropsy calf) at 30wks gestation.
No Significant Findings on clinical examination of 3 of 4 dams. 4th not presented but has history of suspect Theileriosis being investigated.
No gross findings reported.
Histopathology revealed multifocal acute suppurative placentitis and acute focal suppurative myocarditis.
Salmonellosis is caused by a Gram negative rod and is of worldwide concern as a human disease and causes major losses in calves and is an important cause of abortion in cattle and sheep, and in some situations, mares. The organism may be carried by the host without clinical disease and is excreted in saliva, milk, faeces, urine and in fluids discharged when animals abort. Abortion often preceded by a stressful event and usually occurs late in gestation either with no clinical signs or within a week of clinical signs occurring.
Salmonella dublin - associated with pneumonia, abortion and enteritis and polyarthritis.
Pathogenesis: localizes in intestine - bacteraemia and localization in lymph nodes, spleen and lung - growth and second bacteraemia - placentome becomes infected which causes destruction of foetal villi - abortion may occur without invasion of the foetus (live calves can occur but invasion often causes death of foetus)PGF2 alpha release induced by salmonella endotoxin main cause of abortion.
Diagnosis: culture abomasal contents, liver or joints of foetus, placenta, dams faeces, serology, histopathology.
Gross pathology: often retained placenta, foetus autolysed, chorioallantois thickened with amber fibrin containing fluid, yellow exudate on tan or red cotyledons
Histopathology: +/- mineralization, bacterial growth in villi, +/- neutrophil infiltrate+/- multifocal suppurative hepatitis, dilated capillaries may contain many bacteria, necrosis cotyledons
Differentials: Chromosome abnormalities (early) Leptospirosis, BVDV, Theileriosis, acute pyrexic illness, Neosporosis, Campylobacteriosis, Mycoplasma sp., Bovine brucellosis (exotic), Trichomoniasis (more rarely), Mycosis.
What was the stressor in this case? Source?
Cultured organism despite antibiotic therapy.