1. Listeriosis: A Case Study Tara A. Tischio ‘15 Colby College Department of Biology Conclusion: The veterinarian of this case should automatically diagnose this as listeriosis due to the characteristic neurologic symptoms, high temperature, leukocytosis, and abortion of the calf. With immediate administration of antibiotics, it is hard to say whether this patient would fully recover. Most likely, some neurological defects might still persist due to incurable damage to the central nervous system. The fetus was aborted as concluded through the lack of movement or response to stimulus during the rectal examination. If left untreated, this cow would have been dead within 1-2 days. Acknowledgements: I would like to thank Dr. Amy McGee, Dr. Jessica Matulis, Dr. Paul Smith, and the entire team at Kennebec Veterinary Services in Oakland, ME. I would also like to thank Professor Frank Fekete and the department of biology at Colby College. References: 1.Radostits, O., C. Gay, K. Hinchcliff, and P. Constable. Elsevier Saunders, Veterinary Medicine: A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats, and Horses. 2007. p 805-810. 2.Smith, Bradford P. Large Animal Internal Medicine. Mosby, Elsevier, 2009. p 1045-1047. 3."Multistate Outbreak of Listeriosis Linked to Whole Cantaloupes from Jensen Farms, Colorado." Centers for Disease Control and Prevention. 04 Sept. 2012. 4.Klein, N., P. Schoch, and B. Cunha. "Listeria." Infection Control and Hospital Epidemiology 12.5 (May, 1991): JSTOR.. Case Study: A dairy farmer calls you saying that yesterday one of his cows was acting unusual and separating herself from the herd. Today, one side of her face looks droopy and she seems off balance. When you get to the farm to do your physical exam, the cow’s head is tilted and she is walking in circles. Her temperature is slightly high at 104° F (normal: 101°-103° F). She is 265 days pregnant (gestation period is around 275 days) so you perform a rectal examination and as you touch the calf, there is no response. A test of the cerebrospinal fluid shows high levels of leukocytes and high levels of proteins. Microbiology: Caused by Listeria monocytogenes, a gram-positive, rod- shaped bacterium Facultative anaerobe Can survive at temperatures ranging from -0.4°C – 45°C and a pH range of 4.5 – 9.6 Has the ability to form a biofilm Most suceptible species include ruminants and immuno- compromised individuals Transmission: Due to the ingestion of contaminated silage Infection may also be present in the eye if the animal is burying its head in food containing L. monocytogenes infection can spread from a milking-apparatus into the udder of an animal being milked Listeria has also been found in unpasteurized and uncooked foods such as dairy, meat, fruits, and vegetables Prevention and Treatment: General upkeep of the living environment to prevent the spoilage of silage is necessary to prevent listeriosis The countries that perform routine vaccinations generally see less cases of listeriosis but the vaccination is not highly effective and can cost more than the farmers benefit from performing the vaccination Both penicillin and chlortetracycline work well to treat the infection If neurological damage is too far progressed, the antibiotics will not be enough to cure the diseased animal Signs and Symptoms: High Temperature Vomiting, diarrhea, and other flu-like symptoms Acting unusual and separating from the herd Walking in circles, lack of coordination Aborted fetus within 5-10 days of ingestion due to infection of the endometrium Increased leukocytes Mild acidosis Pathogenesis: The bacteria are ingested into the body and spread through septicemia The infected blood travels throughout the body, infecting other major organs The most common site of infection is the central nervous system, with the forming of micro-abscesses on the brain and on the spinal cord These micro-abscesses cause the circling along with balance issues, cocked head, droopy face, separation from the herd, and generally unusual behavior. When the animal is unable to stay standing, death is usually not far off Figure 1. A sheep with a stereotypical cocked head due to microabscesses on the brain and spinal cord. Figures 2 and 3. Infected animal may lean against objects or circle into corners due to a lack of coordination, which gives listeriosis its more common name, “the circling disease”