High HIV– Trypanosoma cruzi Coinfection Levels in Vulnerable Populations in Buenos Aires,Argentina

Editor: The coinfection of Trypanosoma cruzi and HIV is a relevant clinical event. The goal of this study was to establish the frequency of coinfection in populations at risk for HIV-1 in Argentina. A total of 280 HIV-positive serum samples from HIV seroprevalence studies in HIV at-risk groups were tested for T. cruzi infection. Of those samples, eight were positive for T. cruzi (coinfection rate: 2.9%); six of them came from HIV-positive injecting drug users (IDUs) (rate: 7.8%). In view of these results, all HIV-infected patients in endemic countries should undergo T. cruzi diagnosis.

Chagas disease stands as a relevant chronic infection from a public health point of view, with 6–7 million people infected, mostly in Latin America. Although historically a rural disease, a large amount of people infected with T. cruzi in Argentina have immigrated to urban centers, promoting a coexistence with the mainly urban HIV epidemic. Both infections share some routes of transmission, and also have important effects on their evolution. Fluctuations on T. cruzi parasitemia affect HIV viral loads, and HIV patients with profound immunosuppression may reactivate Chagas disease with brain mass lesions, meningoencephalitis, and/or myocarditis. ¹ In Argentina, the largest studies found coinfection prevalence as high as 4.2%, being higher in IDUs: 8.9%. ² The aim of this study was to detect HIV–T. cruzi coinfection rates in populations at risk for HIV-1 in Argentina.

Serum samples from four HIV seroprevalence studies conducted in Buenos Aires city between 2000 and 2004 in different HIV at-risk groups were tested for T. cruzi infection. Studied groups were 174 IDUs, 504 noninjecting cocaine users (NICUs), 801 patients from sexually transmitted infection (STI) clinics, and 1,571 men who have sex with men (MSM). Members of each group were exclusive to the behaviors that characterized them, and were excluded from the study if they referred more than one risk behavior. The HIV infection rate for each group was IDUs, 44.3%; NICUs, 6.3%; STI, 7.4%; and MSM, 10.3%. From those studies, a group of HIV-infected samples were randomly selected to be tested for T. cruzi. The studies were approved by the ethics committees from each institution, and informed consent was obtained from the volunteers.

Plasma samples were analyzed for detection of HIV, HBV, HCV, HTLV-I, and HTLV-II, as described before. ³ T. cruzi infection was detected with EIA (enzymatic immunoassay), IHA (indirect hemagglutination assay), and IFA (indirect immunofluorescence assay), using “in-house” antigens. ⁴ Subjects positive on at least two of these tests were considered to be infected. Categorical variables between two groups were compared using Fisher's exact test. Data were entered and analyzed using InfoStat version 2015.

A total of 280 HIV-positive serum samples were studied: namely 77 IDUs, 28 NICUs, 51 STI patients, and 124 MSM. Of those, eight were positive for T. cruzi, resulting in a coinfection rate of 2.9%; six came from IDUs, and two from STI samples, giving a coinfection rate of 7.8% and 3.9% in each group. Comparing T. cruzi infection between IDUs and non-IDUs (all other groups combined), a significant difference was observed (p = .006, see Table 1).

Needle sharing could have a significant role in Chagas disease spread, especially in nonendemic areas. Similar to previous reports, we found a significantly higher rate of T. cruzi infection in IDUs, ² highlighting the relationship between injecting drug use and Chagas transmission in HIV-infected patients, as with other blood-related infectious diseases such as HCV, HBV, and HTLV-II.

In view of the submitted results, we believe that HIV-infected IDU patients should undergo T. cruzi detection; further studies may show other at-risk populations.