Key aspects of 36 mosquito-borne arboviruses indigenous to Africa are summarized, including lesser or poorly-known viruses which, like Zika, may have the potential to escape current sylvatic cycling to achieve greater geographical distribution and medical importance. Major vectors are indicated as well as reservoir hosts, where known. A series of current and future risk factors is addressed. It is apparent that Africa has been the source of most of the major mosquito-borne viruses of medical importance that currently constitute serious global public health threats, but that there are several other viruses with potential for international challenge. The conclusion reached is that increased human population growth in decades ahead coupled with increased international travel and trade is likely to sustain and increase the threat of further geographical spread of current and new arboviral disease.

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The pesticide DDT [1,1,1‐trichloro‐2,2‐bis(chlorodiphenyl)ethane] is 1 of the 12 persistent organic pollutants (POPs) under negotiation at the Stockholm Convention to restrict or ban their production and use because of their toxicity, resistance to breakdown, bioaccumulation, and potential for being transported over long distances. DDT has estrogenic potential, and the main metabolite,p,p′‐dichlorodiphenyl‐dichloroethylene (p,p′‐DDE), is a potent antiandrogen. In response to mounting evidence on the endocrine‐disrupting influence of environmental chemicals on human health, this epidemiological study was initiated to test the hypothesis that nonoccupational exposure to DDT affects male reproductive parameters. In a cross‐sectional study, healthy male subjects (n = 311) between 18 and 40 years (23 ± 5) of age were recruited from 3 communities in an endemic malaria area in which DDT is sprayed annually. A semen analysis according to World Health Organization (WHO) standards was performed. The Hamilton Thorne Computer Assisted Sperm Analysis (CASA) system was simultaneously used to determine additional sperm motility parameters. Blood plasma samples were assayed forp,p′‐DDT and metabolites as a measure of exposure. The exposure levels were expressed as lipid‐adjustedp,p′‐DDT andp,p′‐DDE values. The meanp,p′‐DDT andp,p′‐DDE concentrations were 90.23 μg/g(±102.4) and 215.47 μg/g(±210.6), respectively. The multivariate linear regression analyses indicated that mean CASA motility was lower with a higherp,p′‐DDE concentration (β = −0.02,P= .001) and the CASA parameter beat cross‐frequency (BCF) was higher with a higherp,p′‐DDT concentration (β = 0.01,P= .000). There was also a statistically significant positive association between percent sperm with cytoplasmic droplets andp,p′‐DDT concentration (β = 0.0014,P= .014). The ejaculate volume (mean 1.9 ± 1.33 mL) was lower than the normal range (≥2.0 mL) according to WHO, and a significant decrease with increasingp,p′‐DDE values was seen for both square root—transformed volume (β = −0.0003;P= .024) and count (β = −0.003;P= .04). Although there were no associations between eitherp,p′‐DDT orp,p′‐DDE concentrations and the rest of the seminal parameters, the incidence of teratozoospermia (99%; normal sperm <15%) was high. Twenty‐eight percent of the study group presented with oligozoospermia (<20 × 10⁶sperm/mL), which had a significant positive association withp,p′‐DDE (odds ratio [OR] = 1.001,P= .03). There was a significant positive association between participants with asthenozoospermia (32%) andp,p′‐DDT (OR 1.003,P= .006) andp,p′‐DDE (OR 1.001,P= .02). The results imply that nonoccupational exposure to DDT is associated with impaired seminal parameters in men. The high exposure levels ofp,p′‐DDT andp,p′‐DDE are of concern because these levels could have far‐reaching implications for reproductive and general health.

In response to mounting concerns about the endocrine‐disrupting influence of environmental chemicals on human health, this epidemiological study was initiated to test the hypothesis that nonoccupational exposure to the estrogenic pesticide 1,1,1‐trichloro‐2,2‐bis(chlorodiphenyl)ethane (DDT) affects male reproductive parameters. One hundred and sixteen men aged 27 years (SD = 8.2) living in malaria endemic‐areas in Chiapas (Mexico), where DDT was sprayed until 2000, participated in a cross‐sectional study. Semen analyses were conducted according to World Health Organization methods and a quality control program was followed. DDT exposure was defined as the level of blood plasmap,p′‐dichlorodiphenyl dichloroethylene (DDE), the major metabolite of DDT. Thep,p′‐DDE concentration adjusted for total lipids was 100 times higher than that reported for nonexposed populations at 45 plus or minus 32 μg/g (mean ± SD). Crude regression analysis showed that several sperm motion parameters, including the percentage of motile sperm, decreased with higherp,p′‐DDE concentrations (β = −8.38;P= .05 for squared motility), and the percentage of sperm with morphological tail defects increased with higher plasmap,p′‐DDE concentration (β = 0.003;P= .017). Insufficient sperm chromatin condensation was observed in 46.6% of participants, and the most severe category of incomplete DNA condensation was also positively correlated withp,p′‐DDE concentration (r= .223;P= .044). Therefore, nonoccupational exposure to DDT, as assessed by plasmap,p′‐DDE concentrations, is associated with poorer semen parameters in men, indicating adverse effects on testicular function and/or the regulation of reproductive hormones. Previously, a causal role of environmental toxicants in human male infertility has been lacking because observed effects have been the result of unusually high exposures, either occupationally or as a result of industrial accidents, resulting in unprecedented controversy (reviewed by Cheek & McLachlan, Environmental hormones and the male reproductive system.J Androl. 1998;19:5). This is the first epidemiological study demonstrating effects after nonoccupational exposures to DDT. Based on these findings, the effect of DDT on male reproductive health should not be ignored.