Molecular epidemiology of ascariasis: a global perspective on the transmission dynamics of Ascaris in people and pigs.

BACKGROUND: The roundworm Ascaris lumbricoides infects 0.8 billion people worldwide, and Ascaris suum infects innumerable pigs across the globe. The extent of natural cross-transmission of Ascaris between pig and human hosts in different geographical settings is unknown, warranting investigation. METHODS: Adult Ascaris organisms were obtained from humans and pigs in Europe, Africa, Asia, and Latin America. Barcodes were assigned to 536 parasites on the basis of sequence analysis of the mitochondrial cytochrome c oxidase I gene. Genotyping of 410 worms was also conducted using a panel of microsatellite markers. Phylogenetic, population genetic, and Bayesian assignment methods were used for analysis. RESULTS: There was marked genetic segregation between worms originating from human hosts and those originating from pig hosts. However, human Ascaris infections in Europe were of pig origin, and there was evidence of cross-transmission between humans and pigs in Africa. Significant genetic differentiation exists between parasite populations from different countries, villages, and hosts. CONCLUSIONS: In conducting an analysis of variation within Ascaris populations from pig and human hosts across the globe, we demonstrate that cross-transmission takes place in developing and developed countries, contingent upon epidemiological potential and local phylogeography. Our results provide novel insights into the transmission dynamics and speciation of Ascaris worms from humans and pigs that are of importance for control programs.

Elimination of lymphatic filariasis: do we have the drugs to complete the job?

PURPOSE OF REVIEW: Lymphatic filariasis is targeted for elimination globally through mass drug administration (MDA) with diethylcarbamazine or ivermectin monotherapy, or either drug in combination with albendazole. However, many countries that have implemented MDA annually for over 5 years are yet to interrupt transmission. This review describes the current drugs used in MDA and highlights the challenges facing the WHO Global Programme to Eliminate Lymphatic Filariasis (GPELF). RECENT FINDINGS: Current drugs used for MDA implementation by national elimination programmes only temporarily clear microfilariae without killing all adult worms. Generally, reports of serious adverse events associated with MDA for lymphatic filariasis using current drugs are uncommon. However, in areas in Africa where lymphatic filariasis co-exists with Loa loa, progressive neurologic decline and encephalopathy within a few days of taking ivermectin have caused great concern. Doxycycline, which is effective at eliminating the Wolbachia symbiont from the lymphatic filariasis parasite, is showing promise as an alternative treatment option for areas where lymphatic filariasis is co-endemic with Loa loa. SUMMARY: Alternative and effective MDA regimens and strategies will be needed if the GPELF is to achieve the goals of global elimination of lymphatic filariasis by 2020. Further research to test new drug regimens (including single high doses of albendazole) or alternative treatment regimens (including biannual treatment schedules) may also be necessary. A new drug, moxidectin, which is currently under development for use against onchocerciasis, may be effective against lymphatic filariasis.

Visceral leishmaniasis cyclical trends in Bihar, India - implications for the elimination programme.

Background: Visceral leishmaniasis (VL) is a vector-borne disease of public health importance in India, with the highest burden of disease in the states of Bihar, Jharkhand, West Bengal and Uttar Pradesh. The disease is currently targeted for elimination (annual incidence to less than one per 10,000 population) using indoor residual spraying, active case detection and treatment. Historically the disease trend in India has been regarded as cyclical with case resurgence characteristically occurring every 15 years.  Understanding this pattern is essential if the VL elimination gains are to be sustained. To better understand the cyclical trends, annual climatic indicators including rainfall, temperature and humidity over time were compared with annual VL case incidence data.  Methods: Annual climate data (rainfall, average and maximum temperature and specific humidity) from 1956-2004 were used to identify potential factors influencing VL incidence.  Months relevant to the VL life-cycle were identified and defined (Monsoon, Sand-fly Peak, Pre-Sand-fly Peak and Annual) for analysis. The Kruskall-Wallis test was used to determine significant difference between categorical rainfall and VL incidence, whilst univariate negative binomial regression models were used to determine predictors of disease incidence. Results: The negative binomial regression model showed statistically significant associations (p <0.05) for VL incidence and maximum temperature, and average temperature, when considering annual and pre-sand fly peak time periods. No other associations between humidity, rainfall or temperature and VL incidence were detected (all values p >0.05).  Conclusion: The VL programme in Bihar has made significant progress in adopting best practices for improved treatment and vector control, with the aim to achieve VL elimination.  However, open access granular programme data for indoor residual spray activities and case detection is required to fully understand the role of climate in disease transmission and potential resurgence.

Adaptation of a malaria surveillance system for use in a visceral leishmaniasis elimination programme.

Background: Successful public practice relies on generation and use of high-quality data. A data surveillance system (the Disease Data Management System [DDMS]) in use for malaria was adapted for use in the Indian visceral leishmaniasis elimination programme. Methods: A situational analysis identified the data flows in current use. Taxonomic trees for the vector of visceral leishmaniasis in India, Phlebotomus argentipes, were incorporated into the DDMS to allow entry of quality assurance and insecticide susceptibility data. A new quality assurance module was created to collate the concentration of DDT that was applied to walls during the indoor residual spraying (IRS) vector control programme. Results: The DDMS was implemented in Bihar State and used to collate and manage data from sentinel sites in eight districts. Quality assurance data showed that DDT was under-applied to walls during IRS; this, combined with insecticide susceptibility data showing widespread vector resistance to DDT prompted a national policy change to using compression pumps and alpha-cypermethrin insecticide for IRS. Conclusions: The adapted DDMS centralises programmatic data and enhances evidence-based decision making and active policy change. Moving forward, further modules of the system will be implemented, allowing extended data capture and streamlined transmission of key information to decision makers.

Soil transmitted helminths and scabies in Zanzibar, Tanzania following mass drug administration for lymphatic filariasis--a rapid assessment methodology to assess impact.

BACKGROUND: Ivermectin and albendazole are used in annual mass drug administration (MDA) for the lymphatic filariasis elimination programmes in African countries co-endemic for onchocerciasis, but have additional impact on soil transmitted helminths and the ectoparasitic mite which causes scabies. Assessing these collateral impacts at scale is difficult due to the insensitivity of available parasite detection techniques. METHODS: The numbers of cases diagnosed with intestinal helminths and scabies and who received prescriptions for treatment were evaluated in 50 health centres in Zanzibar. Records were examined from 2000, prior to the initiation of MDA to 2005, after six rounds of MDA for lymphatic filariasis had taken place. RESULTS: Health centre records showed a consistent decline in the number of cases of intestinal helminths and scabies diagnosed by community health workers in Zanzibar and the number of prescriptions issued across five age groups. A 90-98% decline in soil transmitted helminths and 68-98% decline in scabies infections were recorded. Poisson regression models aggregated to both the island-level and district-level indicated that the decline was statistically significant. CONCLUSIONS: The described method of examining health centre records has the potential for use on a large scale, despite limitations, as a rapid method to evaluate the impacts resulting from both lymphatic filariasis and onchocerciasis MDA. This would result in a reduction in the need for parasitological evaluations to determine prevalence and intensity.