Systematics and biology of Phlebotomine sandflies of the Visceral Leishmaniasis foci of Northern Pakistan
Mohammad Arif, Munir
The aim of this study was to incriminate the vector (s) of visceral leishmaniasis\ud in Northern Pakistan. Two contrasting disease foci were studied- Azad Jammu &\ud Kashmir (AJK) and Northern Areas (NA) through monthly sampling.\ud Studies on the systematics defined morphologically variable species of the\ud subgenera Phlebolomus (Larrousslus) and P. (Adlerius). Morphological characters\ud of all the species belonging to these subgenera were intensively studied. The species\ud belonging to the subgenus Phlebotoinus (Larroussius) were identified as P. major,\ud P.keshishiani, P.kandelakii burneyi and P. spA. and those belonging to subgenus\ud Alderius as P.hindustanicus and P. salangensis. Species belonging to other subgenera.\ud P (Phlebotomus) papatasi, P (Paraphlebtomus) sergentli and P (Paraphlebtomus)\ud alexandri were easily identified.\ud The longitudinal entomological studies were carried out in Bagh district (Rehra\ud village) in AJK and Chilas district (Hudur village, 1200m and Thor village, 1700m)\ud in Northern Areas between April 1991 and November 1991 and in the same months\ud in 1992. Sampling was done using CDC-light traps, sticky-paper traps and mouth\ud aspirators. In addition, a general survey was also undertaken at higher altitudes in\ud Northern Areas and AJK.\ud A total of 9656 Phlebotomus sandflies were collected (8797 during the\ud longitudinal studies and 859 during the general survey). Nine species of Phlebotomus\ud were found,Phlebotomus (A) salangensis for the first time and a new species P.\ud (Larroussius) sp. A. The species composition and relative abundance of species differed\ud within and between the two areas. In Northern Areas P. papatasi (35.75%) followed\ud by P. sergenti (19%) were dominant at the lower altitude of Hudur village but\ud P. keshishiani (29.66%) was most abundant at the higher altitude of Thor village,\ud whereas in AJK, P. hindustanicus (64.62%) was predominant.\ud Species differed in their seasonal abundance. In Northern Areas P. papatasi and\ud P. sergenti showed peak activity in June and July and P. keshishiani in August. In AJK\ud P.hindustanicus showed a clear peak in June preceding the monsoon. The activity was\ud found to be positively correlated with temperature in Northern Areas and negatively\ud correlated with rainfall in AJK.\ud The dominant anthropophilic species included P. papatasi at lower altitudes\ud (Hudur village), P.keshishiani at higher altitudes (Thor village) in Northern Areas and\ud P.hindustanicus in AJK. Most biting occurred around midnight between -2200-2400\ud hours with a second peak between 0400-0600 hours in Northern Areas. None of the\ud sandflies were found biting human volunteers in AJK. Blood-meal analysis revealed\ud that the dominant species P.papatasi, P. sergenti, P. keshishiani and P. hindustanicus\ud have a range of hosts mainly human, bovines and dogs. Monthly sampling with dog\ud baited traps also showed P. keshishiani and P. hindustanicus as the dominant species\ud attracted to the potential reservoir host (dog).\ud Females of P.keshishiani (754), P. salangensis (36), P. alexandri (15) and\ud P.hindustanicus (301) were dissected for natural infections with Leishmania\ud promastigotes and squash blots probed by Leishmania infantum specific DNA probe\ud (LUCA D2 200 BP). Only P.hindustanicus was found to be naturally infected with\ud Leishinania infantum, (parasites identified by DNA hybridization) in AJK. This species\ud is the principal vector involved in the transmission of VL in AJK.\ud From ecological studies it is concluded that the transmission of visceral\ud leishmaniasis takes place at higher altitudes in Northern Areas and that P. keshishiani\ud is the vector.
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