Streit

Epidemiology and Control of Mosquito-Transmitted Pathogens

Thomas G. Streit

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Associate Professional Specialist

My research activities are primarily field-based in Haiti, W.I., and include collaborative efforts with ministry officials in the neighboring Dominican Republic and potential future work in Guyana. I have an appointment at the University which allows for up to eight months each year posted off campus, in the field. In the tropical milieu of Haiti, a setting endemic for three of the world’s major vector-borne diseases, collaborative efforts between Notre Dame, the federal Centers for Disease Control and Prevention, the World Health Organization and its allied Program for Tropical Disease Research, the US Navy, and a private Haitian hospital are focused on the following public health concerns:

1. Lymphatic filariasis, affecting over 120 million persons worldwide, is a disease recently targeted for elimination by the World Health Organization.Haiti suffers from the highest hemispheric prevalence of the disease (up to 60% among focal populations) — and as such is a primary focus of efforts to discern and fine-tune effective elimination strategies over the next five years. Because elimination tools currently available can target only an immature stage of the etiologic agent Wuchereria bancrofti as well as the vector, control and elimination programs will require indicators of success or failure during the very long-term control campaigns necessitated by the 8 year life span of the adult parasite reservoir. I head up one pilot community control program involving mass chemotherapy for interruption of transmission. I am involved in other studies of diagnostic tools for filariasis, drug efficacy trials, community education, immunology and immunopathology of the disease, treatment of gross pathology, and efforts to document possiblesubclinical pathology in infected children. With the likely initiation of regional control programs in Haiti in 1999, the novel application of lot quality assurance methodologies to monitoring parasite infection prevalence in Culex vectors of lymphatic filariasis is a developing area of research. This technique, if found successful, could become a standard tool in the certification of elimination throughout endemic areas worldwide.

2. Our recent serosurveys for dengue antibody prevalence in Haiti have provided preliminary indications that imply transmission rates for these viruses are the highest recorded worldwide. All four dengue serotypes are circulating in the capital Port-au-Prince, a situation which provides a setting for unique opportunities to study transmission dynamics. Planning is underway for analysis of select vector dynamics in this unusual setting. Additionally, a plan to provide documentation for previously hypothesized human racial differences in susceptibility to the more severe hemorrhagic manifestations of dengue infection is under development. Again, with a high incidence and racially stratified population, Haiti lends itself well to such investigation. Finally, I serve as chief of one of two national dengue reference laboratories in Haiti, and epidemiologic surveillance on a national basis is part of a two-fold charge to provide for a domestic diagnostic capability as well.

3. I have participated in preliminary studies to monitor the effectiveness of impregnated bednets at reducing the incidence of falciparum malaria inHaiti, traditionally thought to be the primary cause of febrile episodes. Yet, because CDC quality assurance surveys of laboratories throughout the country found 96% of presumptive cases not to be in fact due to malaria, these studies will evolve into an effort to document any possibly efficacy of impregnated bednets against not only malarial episodes, but also against acute filarial attacks (possibly due to reexposure to infective W. bancrofti larval antigens), and against dengue virus induced fevers.

Collaborative Links with Other Institutions:

Control, Treatment and Prevention of Lymphatic Filariasis in Haiti (Collaborators: D. Addiss, M. Beach, and P. Lammie, CDC Atlanta; M. Milord,Holy Cross Hospital Haiti)

Epidemiology and Elimination of Lymphatic Filariasis in the Dominican Republic (Collaborators: V. Dietz, CDC, Atlanta; G. Gonzalvez and P. Francisco, MOH Dominican Republic) Dengue Epidemiology in Haiti (Collaborators: S. Halstead and D. Watts, US Navy; J. Lafontant, Holy Cross Hospital Haiti; A. Gedeon, MOH Haiti)