Syed Basit Rasheed

Impact of human mobility on the emergence of dengue epidemics in Pakistan

Significance Dengue virus has rapidly spread into new human populations due to human travel and changing suitability for the mosquito vector, causing severe febrile illness and significant mortality. Accurate predictive models identifying changing vulnerability to dengue outbreaks are necessary for epidemic preparedness and containment of the virus. Here we show that an epidemiological model of dengue transmission in travelers, based on mobility data from ∼40 million mobile phone subscribers and climatic information, predicts the geographic spread and timing of epidemics throughout the country. We generate fine-scale dynamic risk maps with direct application to dengue containment and epidemic preparedness. The recent emergence of dengue viruses into new susceptible human populations throughout Asia and the Middle East, driven in part by human travel on both local and global scales, represents a significant global health risk, particularly in areas with changing climatic suitability for the mosquito vector. In Pakistan, dengue has been endemic for decades in the southern port city of Karachi, but large epidemics in the northeast have emerged only since 2011. Pakistan is therefore representative of many countries on the verge of countrywide endemic dengue transmission, where prevention, surveillance, and preparedness are key priorities in previously dengue-free regions. We analyze spatially explicit dengue case data from a large outbreak in Pakistan in 2013 and compare the dynamics of the epidemic to an epidemiological model of dengue virus transmission based on climate and mobility data from ∼40 million mobile phone subscribers. We find that mobile phone-based mobility estimates predict the geographic spread and timing of epidemics in both recently epidemic and emerging locations. We combine transmission suitability maps with estimates of seasonal dengue virus importation to generate fine-scale dynamic risk maps with direct application to dengue containment and epidemic preparedness.

A review of dengue as an emerging disease in Pakistan

The presence of dengue virus has been detected using neutralization and haemagglutination inhibition antibodies in local populations in Pakistan since the 1960s. However, the first epidemic was not reported until 1994. This was followed by some cases in 1995, but the disease was confined to the port city of Karachi. Since 2006, dengue epidemics have occurred every year and the range has extended to most cities in Pakistan. Dengue now affects thousands of people and has caused hundreds of deaths. It has become a major health problem in Pakistan, and it is likely to become an even greater health problem in the coming years. This review gives an insight into the dengue situation from the early 1960s to the most recent epidemics in Pakistan, and also describes the primary vector of this disease (Aedes aegypti) in Pakistan. As such, it provides the first comprehensive review of the emergence of this important public health problem.

Global genetic diversity of Aedes aegypti

Mosquitoes, especially Aedes aegypti, are becoming important models for studying invasion biology. We characterized genetic variation at 12 microsatellite loci in 79 populations of Ae. aegypti from 30 countries in six continents, and used them to infer historical and modern patterns of invasion. Our results support the two subspecies Ae. aegypti formosus and Ae. aegypti aegypti as genetically distinct units. Ae. aegypti aegypti populations outside Africa are derived from ancestral African populations and are monophyletic. The two subspecies co‐occur in both East Africa (Kenya) and West Africa (Senegal). In rural/forest settings (Rabai District of Kenya), the two subspecies remain genetically distinct, whereas in urban settings, they introgress freely. Populations outside Africa are highly genetically structured likely due to a combination of recent founder effects, discrete discontinuous habitats and low migration rates. Ancestral populations in sub‐Saharan Africa are less genetically structured, as are the populations in Asia. Introduction of Ae. aegypti to the New World coinciding with trans‐Atlantic shipping in the 16th to 18th centuries was followed by its introduction to Asia in the late 19th century from the New World or from now extinct populations in the Mediterranean Basin. Aedes mascarensis is a genetically distinct sister species to Ae. aegypti s.l. This study provides a reference database of genetic diversity that can be used to determine the likely origin of new introductions that occur regularly for this invasive species. The genetic uniqueness of many populations and regions has important implications for attempts to control Ae. aegypti, especially for the methods using genetic modification of populations.

Population structure of the mosquito Aedes aegypti (Stegomyia aegypti) in Pakistan

Eleven microsatellite markers were used to determine the genetic population structure and spread of Aedes aegypti (Stegomyia aegypti) (Diptera: Culicidae) in Pakistan using mosquitoes collected from 13 different cities. There is a single genetic cluster of Ae. aegypti in Pakistan with a pattern of isolation by distance within the population. The low level of isolation by distance suggests the long‐range passive dispersal of this mosquito, which may be facilitated by the tyre trade in Pakistan. A decrease in genetic diversity from south to north suggests a recent spread of this mosquito from Karachi. A strong negative correlation between genetic distance and the quality of road connections shows that populations in cities connected by better road networks are less differentiated, which suggests the human‐aided passive dispersal of Ae. aegypti in Pakistan. Dispersal on a large spatial scale may facilitate the strategy of introducing transgenic Ae. aegypti or intracellular bacteria such as Wolbachia to control the spread of dengue disease in Pakistan, but it also emphasizes the need for simple measures to control container breeding sites.

Species Distribution Modelling of Aedes aegypti in two dengue‐endemic regions of Pakistan

Statistical tools are effectively used to determine the distribution of mosquitoes and to make ecological inferences about the vector‐borne disease dynamics. In this study, we utilised species distribution models to understand spatial patterns of Aedes aegypti in two dengue‐prevalent regions of Pakistan, Lahore and Swat. Species distribution models can potentially indicate the probability of suitability of Ae. aegypti once introduced to new regions like Swat, where invasion of this species is a recent phenomenon.

Distribution, species composition and relative abundances of sandflies in North Waziristan Agency, Pakistan

This study was conducted to investigate the diversity of sandflies (Psychodidae: Phlebotominae) and the incidence of leishmaniasis in three villages of North Waziristan Agency, Pakistan. Sandflies were sampled monthly during 2012, at dusk and dawn, in selected indoor habitats including both bedrooms and animal sheds using a knock‐down spray catch method. A total of 3687 sandflies were collected, including 1444 individuals in Drezanda, 1193 in Damdil and 1050 in Dattakhel. This study revealed 14 species of two genera, Phlebotomus (Phlebotomus sergenti, Phlebotomus papatasi, Phlebotomus caucasicus, Phlebotomus kazeruni, Phlebotomus alexandri and Phlebotomus salehi) and Sergentomyia (Sergentomyia dentate, Sergentomyia baghdadis, Sergentomyia babu, Sergentomyia theodori, Sergentomyia sumbarica, Sergentomyia dreyfussitur kestanica, Sergentomyia hogsoni pawlowskyi and Sergentomyia fallax afghanica) (both: Diptera: Psychodidae). Phlebotomus sergenti was the most abundant species (42.1%), followed by S. dentata (17.7%) and S. baghdadis (17.4%). The number of males collected represented about twice that of female flies, and the maximum number was collected in July, followed by August. The determination of the species composition of sandfly populations, seasonal variations, relative abundances and estimations of infection in the vector population may provide information about the dynamics of leishmaniasis transmission that is useful in planning vector control activities.

Evaluation of DNA damage in lymphocytes of radiology personnel by comet assay

Evaluation of DNA damage in lymphocytes of radiology personnel by comet assay: Muhammad Khisroon, et al. Department of Zoology, University of Peshawar, Pakistan

Environmental risk modeling and potential sand-fly vectors of Cutaneous Leishmaniasis in Chitral District: A leishmanial focal point of mount Tirchmir, Pakistan

To provide baseline information about suspected vectors and the incidence, distribution and an active zone of transmission for cutaneous leishmaniasis (CL) in Chitral, Pakistan, using GIS tools; and to investigate the role of environmental factors in the disease dynamics.