Research

Host-parasite interactions in Himalayan Birds

Birds do not leave their parasites behind when they migrate back from their wintering to their breeding grounds. The role of migratory birds to spread diseases between regions has been widely documented; however, the extent to which the parasite diversity and transmission varies between migrant and non-migrant host species has not been adequately explored across an altitudinal gradient in western Himalayas. Many migrants move between altitudes or to the plains, and thereby encounter different faunas of parasites and pathogens compared with resident species. In plains, the resident birds may act as reservoirs for blood parasites, increasing the risk of migrants to become infected with new parasites in wintering ground. Given that suitable vectors are present to transmit and maintain the infection, such migrants can form effective bridge for parasites between wintering and breeding grounds. Hence, increases the risk of infection to naïve resident birds in high-altitude. We aim to explore the degree to which (a) migrant and resident avian hosts are infected with three vector-borne parasite genera Plasmodium, Haemoproteus and Leucocytozoon across altitudes in the western Himalayas, (b) expansion or contraction in geographical or altitudinal ranges of vector communities and consequent risks of parasite transmission in malaria-free zones. We use a wide range of multidisciplinary field and lab analytical techniques (see below).

Hypoxia physiology and Immune genes

Environmental hypoxia - the decreased partial pressure of oxygen - and cold temperature are important physiological stressors on organisms living in a high elevation environment and are the key drivers in the evolution of high elevation adaptations in montane organisms. We are interested in finding out how does migrant birds cope with change in haemoglobin concentration as well as parasite infections acquired during migration journey.

Vector-parasite interactions

Malaria parasites use vertebrate hosts for asexual multiplication and Culicidae mosquitoes and other blood feeding arthropods for sexual and asexual development. We are interested in identifying vector for avian malaria and their host breadth index.

Mistnetting for sampling birds

Birds are caught using mist nets and sampled for parasite DNA isolation. We mark birds with Bombay Natural History Society aluminium rings. Blood sampling can be done quickly (~1 min/bird) and has no ill effect on birds. The longest retrap birds were Rusty-cheeked Scimitar Babbler and Black-chinned Babbler ringed in 2009 and again retrapped in 2015 in Dehradun!!

Host and parasite genetics

The presence of Plasmodium, Haemoproteus and Leucocytozoon is assessed using parasite-specific primers designed to amplify the Cytochrome b gene fragment.

Microscopy for morphology of parasites

To determine the true species composition of the haemosporidians in each naturally infected individual host, a combination of both microscopy and molecular methods is important. We are screening each sampled host species for parasite intensity and parasite identification.

Vector sampling and their genetics

Malaria and related haemosporidian parasites use vertebrate hosts for asexual multiplication and Culicidae mosquitoes and other insect vectors for sexual and asexual development. Using DNA sequencing of the cyt b gene, we are examining the phylogeography and diversity of the parasite lineages found in different vector populations. We dissect salivary glands from mosquito thorax to screen for sporozoites of Plasmodium sp.

Field and Lab techniques

Mistnet set up in the field

Blood smear preparation

Haemoproteus parasite in bird blood smear