By Ethan Covey
Surveillance of toxoplasmosis in the United States is hindered both by the fact that the disease is not nationally reportable, and that definitions used for diagnosis vary considerably within states that track cases, according to a recent report from the CDC.
As of 2021, toxoplasmosis has been reported in Arkansas, Delaware, Hawaii, Kentucky, Minnesota, Nebraska, Pennsylvania and Wisconsin (MMWR Morb Mortal Wkly Rep 2022;71[28]:889-893).
“This report highlighted both the challenges of doing public health surveillance for toxoplasmosis and the variations in the case definitions used by states,” said Anne Straily, DVM, a veterinary medical officer in the CDC’s Division of Parasitic Diseases and Malaria. “Variations in case definitions like those identified in this evaluation are important because it means that we’re not all counting the same thing, which makes it difficult to compare disease prevalence or other factors among states where the disease is reportable.”
Public health representatives from six of the reportable states (Arkansas, Kentucky, Minnesota, Nebraska, Pennsylvania and Wisconsin) participated in a survey conducted from June to July 2021, aimed to clarify how toxoplasmosis surveillance data are collected and utilized.
Much of the sought-after information, such as when toxoplasmosis became reportable in these states and why, was unable to be verified. Multiple potential reasons were given for why the disease had been made reportable, including monitoring disease prevalence, a need to identify the source of infection, the effect of toxoplasmosis on pregnancy, congenital transmission and outbreak identification. However, the anecdotal reasons could not be confirmed.
In addition, definitions regarding what constitutes a case of toxoplasmosis varied greatly among states, with clinical descriptions, laboratory criteria and case classifications all showing broad variance.
“Surveillance data can provide information on potential risk factors for disease, but that will depend on the goals of the surveillance and what data are collected during a case investigation,” Dr. Straily said.
While the lack of national surveillance will likely complicate efforts to appropriately track the disease, the study authors noted that development of standardized case definitions would help ensure that cases are counted consistently.
“When the states that participated in this project learned what each other was doing in terms of surveillance, they recognized there was an opportunity to do things better, so now they’re working to develop a standardized case definition for surveillance for toxoplasmosis,” Dr. Straily added. “A standardized case definition will help ensure that we’re all counting the same thing, so a confirmed case in one state is the same as a confirmed case in another state. That will help us better understand the burden of disease.”
