CASE NOTES
Salmonella Abortion in Dairy Cattle
Andrew Thompson, Veterinary Pathologist, EMAI
Posted Flock & Herd August 2010
Introduction
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.
Post-mortem and pathology findings
No gross findings reported.
Placentome, acute suppurative placentitis with villous destruction
and numerous bacterial colonies
Histopathology revealed multifocal acute suppurative placentitis and acute focal suppurative myocarditis.
Placenta
Serology:
- Pestivirus AGID 2,2,3
- Neospora ELISA negative (x3)
- Leptospira Hardjo and Pomona MAT negative
- Salmonella dublin SAT #2890 20; #2094 80 and #646 < 10
- Salmonella typhimurium #2890 40; #2094 < 10 and #646 < 10
- Bacteriology: Gram stain abdominal fluid: numerous gram negative rods
- Profuse pure and mixed growth of Salmonella dublin from foetal stomach content, foetal lung and placenta # 2890
Discussion
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.
General:
- Zoonosis - isolate animals
- Environmental contamination an issue - survives long time (months)
- Host adapted salmonellae.g.Dublin cattle more likely to develop into a carrier state
- Serology - can be difficult to interpret as immune response depends on whether it is pregnant or not and the stage of gestation; some arbortifacients cause seroconversion before abortion
- Elevated IgG - indicates an active foetal immune response to a foreign antigen (almost always an infectious agent)
- Fluke infestation reported to greatly increase susceptibility of cattle to infection with Salmonella dublin (Aiken et al. 1978)
- Animals treated with antibiotics do not usually yield the organism
What was the stressor in this case? Source?
Cultured organism despite antibiotic therapy.
Reference
- Kennedy, P and Miller, B The female genital system in Jubb, K, Kenendy, P and Palmer, N Pathology of Domestic Animals 4th Edition