Prevention and control of Zika fever as a mosquito-borne and sexually transmitted disease

The ongoing Zika virus (ZIKV) epidemic poses a major global public health emergency. It is known that ZIKV is spread by \textit{Aedes} mosquitoes, recent studies show that ZIKV can also be transmitted via sexual contact and cases of sexually transmitted ZIKV have been confirmed in the U.S., France, and Italy. How sexual transmission affects the spread and control of ZIKV infection is not well-understood. We presented a mathematical model to investigate the impact of mosquito-borne and sexual transmission on spread and control of ZIKV and used the model to fit the ZIKV data in Brazil, Colombia, and El Salvador. Based on the estimated parameter values, we calculated the median and confidence interval of the basic reproduction number R0=2.055 (95% CI: 0.523-6.300), in which the distribution of the percentage of contribution by sexual transmission is 3.044 (95% CI: 0.123-45.73). Our study indicates that R0 is most sensitive to the biting rate and mortality rate of mosquitoes while sexual transmission increases the risk of infection and epidemic size and prolongs the outbreak. In order to prevent and control the transmission of ZIKV, it must be treated as not only a mosquito-borne disease but also a sexually transmitted disease

Sexually transmitted diseases in laboring women: trend over a decade

Background: Center for Disease Control (CDC) recommends routine screening in all pregnant women at first visit for syphilis, HIV, Hepatitis B infection as they have high vertical transmission rate. Syphilis is brought to control by screening and early treatment with penicillin, whereas HIV and Hepatitis B are incurable viral infections till date. Hence prevention is the only way to control the disease in the population. The purpose of the study is to know the burden of sexually transmitted diseases, so that prevention programme is better planned.Methods: This is a retrospective analytical study conducted from January 2005 to December 2014, in Karnataka Institute of Medical Sciences, Hubli, Karnataka. All the patients who delivered in septic ward, who were more than 28 weeks of gestation and who were HIV, HBsAg or VDRL positive were included in the study.Results: Among the total of 79,472 deliveries, the prevalence of HIV, HBsAg and VDRL were 0.90, 1.06 and 0.31 respectively. There were 4 cases of co-infection. The prevalence of HIV was 0.79 in 2005 and reached its peak of 1.33 in 2008 and then showed a steady decrease, reaching a lowest of 0.52 in 2014. The prevalence of HBsAg was 0.70 in 2005 and reached a peak of 1.57 in 2014. The prevalence of VDRL was highest of 0.08 in 2005 and lowest of 0.02 in 2014. Highest operative deliveries were seen in HBsAg positive women. Stillbirths were maximum in VDRL positive women and least in HBsAg positive women. There were 9 maternal deaths in HIV positive women and 3 maternal deaths in HBsAg positive women.Conclusions: In our study HIV prevalence is showing a down trend and syphilis is at the verge of elimination as seen globally. However prevalence of Hepatitis B has shown a rising trend over a decade in our institute, unlike a down trend seen globally. Intensifying the screening of Hepatitis B in pregnancy and Immunisation programme of neonates, reducing overcrowding and providing better living conditions, improving hygiene and health education should be done in order to reduce the prevalence of Hepatitis B infection

Male-killing bacteria in insects: mechanisms, incidence and implications

Bacteria that are vertically transmitted through female hosts and kill male hosts that inherit them were first recorded in insects during the 1950s. Recent studies have shown these "male-killers" to be diverse and have led to a reappraisal of the biology of many groups of bacteria. Rickettsia, for instance, have been regarded as human pathogens transmitted by arthropods. The finding of a male-killing Rickettsia obligately associated with an insect suggests that the genus' members may be primarily associated with arthropods and are only sometimes pathogens of vertebrates. We examined both how killing of male hosts affects the dynamics of inherited bacteria and how male-killing bacteria affect their host populations. Finally, we assessed the potential use of these microorganisms in the control of insect populations

Evolutionary bi-stability in pathogen transmission mode

Many pathogens transmit to new hosts by both infection (horizontal transmission) and transfer to the infected host's offspring (vertical transmission). These two transmission modes require speci®c adap- tations of the pathogen that can be mutually exclusive, resulting in a trade-off between horizontal and vertical transmission. We show that in mathematical models such trade-offs can lead to the simultaneous existence of two evolutionary stable states (evolutionary bi-stability) of allocation of resources to the two modes of transmission. We also show that jumping between evolutionary stable states can be induced by gradual environmental changes. Using quantitative PCR-based estimates of abundance in seed and vege- tative parts, we show that the pathogen of wheat, Phaeosphaeria nodorum, has jumped between two distinct states of transmission mode twice in the past 160 years, which, based on published evidence, we interpret as adaptation to environmental change. The ®nding of evolutionary bi-stability has impli- cations for human, animal and other plant diseases. An ill-judged change in a disease control programme could cause the pathogen to evolve a new, and possibly more damaging, combination of transmission modes. Similarly, environmental changes can shift the balance between transmission modes, with adverse effects on human, animal and plant health