Impact of seasonal variation on Leishmania donovani infection in hamsters.

ABSTRACT

The impact of seasonal variation on the course of L. donovani infection in hamsters was investigated. Though the animals were maintained in controlled climatic conditions (25 degrees C +/- 2), parasites exhibited seasonal rhythm. During summer (April-July) when the atmospheric temperature ranged from 20.5 degrees C to 41.8 degrees C, the parasite load from an inoculum of 1 x 10(7) amastigotes/animal was found to be less than 1 to 9 per 100 cell nuclei (based on spleen biopsy) on day 25-35 post infection. An escalation in count was observed from August onwards, which reached the peak (approximately 30/100 cell nuclei) in February-March (temp. range 11.3 degrees C to 31.4 degrees C). The multiplication rate monitored 15 days after the initial assessment also showed a similar pattern. The secondary organs examined showed no parasites. The study revealed that despite the non-involvement of the vector in experimental infection in hamster, the parasites retained its periodic character as in man, corresponding to cyclicity of vector.