Quantifying Effect of Geographic Location on Epidemiology ofPlasmodium vivaxMalaria

Abstract

Recent autochthonous transmission of Plasmodium vivax malaria in previously malaria-free temperate regions has generated renewed interest in the epidemiology of this disease. Accurate estimates of the incubation period and time to relapse are required for effective malaria surveillance; however, this information is currently lacking. By using historical data from experimental human infections with diverse P. vivax strains, survival analysis models were used to obtain quantitative estimates of the incubation period and time to first relapse for P. vivax malaria in broad geographic regions. Results show that Eurasian strains from temperate regions have longer incubation periods, and Western Hemisphere strains from tropical and temperate regions have longer times to relapse compared with Eastern Hemisphere strains. The diversity in these estimates of key epidemiologic parameters for P. vivax supports the need for elucidating local epidemiology to inform clinical follow-up and to build an evidence base toward global elimination of malaria.

Do hypnozoites cause relapse in malaria?

“…Consider the time interval to the first P. vivax recurrence following a primary infection. It is highly variable [31] but often about 3 weeks [32]. Accordingly, some early homologous P. vivax recurrences could perhaps prove to have skin stages rather than intrahepatocytic hypnozoites as their origin [28,29].…”

“…Recurrences aside, where do the parasites live that are responsible for long incubation periods, not only in P. falciparum and P. malariae malaria, but also in P. vivax (e.g., [31,45]) and P. ovale (e.g., [41,[46][47][48][49]) infections? Moreover, are the persisting parasites sporozoites, hypnozoites, merozoites, or more than one of these?…”

Decision letter: Modelling the contribution of the hypnozoite reservoir to Plasmodium vivax transmission

“…The red curves show the model fits with estimated posterior median parameters. DOI: 10.7554/eLife.04692.003 The following figure supplement is available for figure 1: obtainable via survival analysis of patient data (Lover and Coker, 2013;Battle et al, 2014) (Figure 3C,D). The expected number of relapsing hypnozoites per individual is expected to follow an approximately exponential distribution ( Figure 3E,F) in agreement with empirical observations (Horing, 1947;White, 2011).…”

“…There is considerable geographical variation in the timing and frequency of P. vivax relapse infections, with strains from tropical areas having an average time to first relapse of 3-6 weeks and longlatency strains from temperate areas relapsing within 6-9 months (Lover and Coker, 2013;Battle et al, 2014). Beyond the first relapse, periodic patterns in multiple relapses from a single mosquito bite have been observed (White, 2011).…”

Global infectious diseases—The new norm for the United States?

“…Although great strides have been made over the last 20 years, including the ability to describe the etiology of a variety of disease states by the same pathogens and symptom syndromes that previously remained mysteries without clear-cut etiologies, including parvovirus B19, cytomegalovirus (CMV), Epstein-Barr virus (EBV) and others, pathogens and the vectors that facilitate their Clearly there are many pathogens to discuss, and train for in the US, but we would be remiss to ignore the most significant infectious diseases-ones that impact large populations and cause serious illness, such as malaria, 39 dengue, tuberculosis, 40,41 HIV/AIDS, and influenza, among the most important. Respiratory infections (upper and lower tract) can readily be spread airborne.…”