Toxoplasmosis outbreak associated with Toxoplasma gondii-contaminated venison—high attack rate, unusual clinical presentation, and atypical genotype

Authors: SHCUMACHER, AMY - Centers For Disease Control And Prevention (CDC) - United States; MONTOYA, JOSE - Palo Alto Medical Foundation Toxoplasma Serology Laboratory; KAZMIERCZAK, JAMES - Wisconsin Department Of Health Services; PRESS, CYNTHIA - Palo Alto Medical Foundation Toxoplasma Serology Laboratory; STRAILY, ANNE - Centers For Disease Control And Prevention (CDC) - United States; AJZENBERG, DANIEL - Centers For Disease Control And Prevention (CDC) - United States; DARDE, MARIE-LAURE - National Reference Center For Toxoplasmosis; PASSEBOSC-FAURE, KARINE - Centers For Disease Control And Prevention (CDC) - United States; GOMEZ, CARLOS - Palo Alto Medical Foundation Toxoplasma Serology Laboratory; MOLDENHAUER, ELLEN - Jackson County Health And Human Services; HANDLY, TAMMY - Jackson County Health And Human Services; Hill, Dolores; LETZER, DAVID - Infectious Disease Specialists Of Southeastern Wisconsin; ELBADAWI, LINA - Centers For Disease Control And Prevention (CDC) - United States; DESALVO, TRACI - Wisconsin Department Of Health Services; SMILEY, STEPHANIE - Wisconsin Department Of Health Services

Submitted to: Clinical Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2020
Publication Date: 5/15/2020
Citation: Shcumacher, A., Montoya, J.G., Kazmierczak, J., Press, C., Straily, A., Ajzenberg, D., Darde, M., Passebosc-Faure, K., Gomez, C.A., Moldenhauer, E., Handly, T., Hill, D.E., Letzer, D., Elbadawi, L.I., Desalvo, T., Smiley, S. 2020. Toxoplasmosis outbreak associated with Toxoplasma gondii-contaminated venison—high attack rate, unusual clinical presentation, and atypical genotype. Clinical Infectious Diseases. 72(9):1557-1565. https://doi.org/10.1093/cid/ciaa285.
DOI: https://doi.org/10.1093/cid/ciaa285

Interpretive Summary: Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is a leading foodborne cause of death in the United States.1 Identified in 1939 as a causative agent for certain birth defects,2,3 T. gondii can infect any warm-blooded animal, although its definitive hosts are the Felidae.4 Most healthy individuals suffer subclinical infections, but severe sequelae such as chorioretinitis can occur. The genetic diversity of T. gondii has been the subject of much research, as geographic variation in strain has led to apparent variation in the clinical presentation of toxoplasmosis across the globe.6-8 Recent genotyping research divides T. gondii strains into haplogroups that correspond to and expand beyond the previous strain classification system,9 although more research is needed to understand variations in clinical manifestations by haplogroup.10 Haplogroup 129 is the dominant strain in North American wildlife.11 As such, a better understanding of the clinical manifestations of haplogroup 12 could aid health care providers in identifying cases of toxoplasmosis. We describe an outbreak of toxoplasmosis among 9 of 11 men who consumed undercooked venison infected with T. gondii haplogroup 12 cysts. The epidemiologic and laboratory (serologic, histologic, and genotypic) investigations are presented; implications for medicine and public health are discussed.

Technical Abstract: Background: In October 2017, a physician contacted the Wisconsin Division of Public Health (WDPH) regarding a patient with fever, myalgia, leukopenia, and thrombocytopenia of undetermined etiology. An investigation identified the illness as toxoplasmosis following venison consumption during a retreat at which 11 other individuals were present. We investigated to determine outbreak magnitude and illness-related factors. Methods: We interviewed all attendees and coordinated Toxoplasma gondii testing. A confirmed toxoplasmosis case was defined as fever, fatigue, muscle aches, or sweats (=3 symptoms) with onset during October 3 -21 and serologic test results consistent with recent T. gondii infection. Testing of human sera and venison were completed by national reference laboratories in the United States and France. Relevant medical records were abstracted. Results: All 12 attendees were male; median age was 51 (range: 22 -75) years. Ten of 11 attendees who consumed the never-frozen, locally harvested venison reported it was definitely or possibly undercooked. A median of 7 days after exposure, 9 of 11 developed confirmed illnesses lasting a median of 12 days; all 9 sought outpatient health care. Bloodwork was somewhat atypical for toxoplasmosis. Three attendees were not ill --2 (1 unexposed) had no serologic evidence of infection; the third had serologic evidence of immunity. Venison tissue sections demonstrated a high parasite load; T. gondii DNA was detected in the venison by PCR and genotyped as haplogroup 12. Conclusions: Evidence implicated consumption of undercooked venison as the illness source. High parasite load and T. gondii haplogroup might explain the high attack rate.