[leish-l] Zoonotic cutaneous leishmaniasis in Pakistan

[BobKillick-Kendrick]

Parasites causing CL in Balochistan  have been typed as L. major and, from the landscape epidemiology, the reservoir will be gerbils, the vector will be P. papatasi (and perhaps the closely related species P. salehi in Sindh) and the disease is Old World zoonotic cutaneous leishmaniasis (ZCL) which, in most cases, will self cure in 6 months leaving the patient immune to a further episode. (CL caused by L. tropica, which occurs in other parts of Pakistan, is another story.) There has been a high prevalence clinically recognisable ZCL recorded in this province every year for many years. Perhaps it is exaggerating to say there is an outbreak at the moment, when nothing has changed.  Aerial spraying should not even be considered. It is not cost effective, it cannot be maintained and it is probably disastrous for the population dynamics of sand flies. Virtually nothing is known of the predators of sand flies but there must be some that are doing a good job - or we'd be knee deep in sand flies. Spraying will kill predators and, when spraying stops, it is very unlikely they will recover as fast as the sand flies. The immune proportion of the human population will have fallen, the population of vectors will have risen, and a real epidemic can be expected. WHO recommended short term spraying only when there is an epidemic of a life threatening form of leishmaniasis such as kala-azar in the Indian subcontinent. With regard to house spraying, it is not a fair comparison to assume that house spraying against P. papatasi would be as effective as it appears to have been against P. argentipes, the Indian vector of visceral leishmaniasis. The behaviour of the P. papatasi is totally different from that of the Indian fly and I know of no instance where house spraying against Old World ZCL has been shown to be cost-effective. (Please correct me if I'm wrong.) The only real success story I know of is the destruction of the habitat on the steppes of Central Asia followed by planting rice, cotton or winter wheat to prevent reversion to the original conditions (which later turned out to be an environmental catastrophe for the Aral Sea). ZCL of the Old World, although a public health problem, is not life-threatening and in some countries it is left to run its natural course except with patients with multiple lesions or with lesions in dangerous places such as the nose, eyelid etc. If that sounds unsympathetic and cruel, all I can say is that's how Tony Bryceson 'treated' me when I had ZCL. 
Bob Killick-Kendrick
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