TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE (1996) 90, CORRESPONDENCE 717

lCorrespondencel ‘0 come, let us wallow in glorious mud’*

I read with interest the report of failure of passive zoo- prophylaxis in Pakistan and the association between cat- ile bwnership and higher malaria prevalence (Bouma & Rowland. 1995: Transactions, 89. 351X However. the chief veciors of malaria in Pakistan, An&&s cuZi&cies and A. stephensi, feed primarily on water buffaloes and are highly attracted by them, being easily collected at resting sites in or near buffalo huts (Reisen & Boreham, 1982: Journal of Medical Entomology, 19, 98). In a pre- vious report we noted that a switch from primary buffalo feeding to feeding on humans occurred at the time of year when plentiful surface mud made it possible for buffaloes to wallow in mud holes and cover their hides, including the preferred mosquito biting sites (under- belly, teats, ankles), with a thick layer of dry, caked mud (Nalin & Mahmood, 1983: Proceedings of the Third &XAC Conference, 2s October 1983, Las Vigas, Nevada [ISSN 0733-63731, abstract no. 172). The theory was ad- vanced that this feeding switch from water buffaloes to humans was very probably triggered by the inability to find biteable buffaloes during the malaria transmission season, when mud coating of the buffaloes makes them unavailable to feeding anophelines. It was suggested that washing the buffaloes to maintain them free of mud at that time of year, or otherwise preventing them from mud-coating themselves, might result in reduced ma- laria transmission.

Thus, the association between cattle (buffalo) owner- ship and higher malaria prevalence is not surprising; buffaloes are part of the vector bioecological system in Pakistan and owning buffaloes results in higher vector density in the immediate environment. It is still likely, however, that intervention which could prevent seasonal mud-coating would result in reduced transmission, and this deserves a controlled field test. Zooprophylaxis may well play a useful role if the buffalo mud factor is recog- nized and addressed, even though an effect on transmis- sion and incidence may’ be demonstrable sooner and more easily than an effect on prevalence, which is of course determined by prior infections. An effect of buf- falo washing on malaria prevalence would require a longer period of follow-up to detect.

Clinical Research Merck Research Laboratories P.O. Box 4, BL 3-4 West Point PA 19486, USA

David R. Nalin

lOJune 1996

‘0 come, let us wallow...‘. A reply Muddying the waters, or turning zooprophylaxis from failure to success

The standard practice of bathing water buffalo in muddy pools may conceivably form a mud coating which acts as a partial barrier to mosquito biting. Unfor- tunately, Afghan refugees in our study area keep only cattle and not water buffalo, and cattle do not require regular bathing during the hot summers. Local Paki- stanis keep both cattle and buffalo, but our observations are that the mud layer is imperfect and mosquitoes have little trouble in feeding. In fact. cattle and buffalo are re- markably inept at de&ring biting, unlike humans, or goats and sheep which can ‘flex’ their hairy skins. Hence cattle and buffalo are largely responsible for amplifying

*This phrase is derived from a song popularized by the late M. Flanders and D. Swann in the UK several decades ago (editor).

mosquito populations. A mud barrier might, in the short term, deflect mosquitoes on to humans and increase ma- laria transmission but, in the medium term, mosquito densities and malaria should decrease because of the dif- ficulty mosquitoes have in obtaining blood. Thus we oredict the ouuosite: ‘clean’ cattle and buffalo amolifv ;nosquito poiilations and increase malaria, muddy-cat- tle and buffalo might conceivably reduce mosquito populations and reduce malaria. But a more realistic so- lution than mud, at least for Afghans, might be treat the skins of their cattle with an insecticide that is safe for mammals. Permethrin, applied in this way, does control anouhelines for a while (McLaughlin et aZ.. 1989: 7ournal of tie American Mosquito‘ControlVAssociatio& 5, 607, and a pilot project currently under way in the North-West Frontier Province indicates major reductions in mos- quito and tick densities, and in malaria incidence, plus the added benefit of healthier cattle whose extra produc- tivity in milk and meat outweighs insecticide costs. This exciting new malaria control strategy is potentially much more cost-effective and sustainable than the house spraying traditional to the area.

Health Net International P.O. Box 889 Peshawar Pakistan

Mark Rowland Sean Hewitt

Menno Bouma

I6July 1996

When injections are not necessary In developing countries the use and overuse of syr-

inges and needles is a major health hazard, especially for children. Lack of money, electricity cuts, poor training and disbelief in ‘germs’ have led to tolerance of unsterile injections even in hospitals. In the Ebola virus epidemic in Zaire in 1976, hospitals were epidemic amplifiers: 72 of 103 primary cases were caused by unsterile injections in Yambuku mission hosuital. The risk of Ebola virus infection from a single injection was greater than 90% (Garrett, 1994: The Coming Plague. New York: Farrar, Straus & Giroux**).

As well as working towards sterile injections, the very use of injections must be discouraged. Practice can be changed. Only a decade ago, under the threat of HIV and AIDS, doctors in Africa were able to halve the number of blood transfusions to children immediately. All injections must be sterile and their number reduced. The health services must set an example for those in pri- vate practice.

Recent studies question the assumption that intra- muscular injection delivers a drug more effectively. In- tramuscular injection for malaria is the most likely treat- ment when vomiting prevents oral treatment. However, oral treatment of unconscious children with chloroquine by nasogastric tube is cheaper and spares the child the risk of poliomyelitis, injeciion abscesses, hepatitis, etc. (Neeauave et aZ., 1991: Transactions. 85. 718). Treatment by re&n with buinimax’”

I , or qui&ne has been success-

ful in Sierra Leone (Westman et al., 1994: Transactions, 88, 446), Madagascar (Barennes et al., 1993; Midecine d’A&ue Noire, 40, 401), Niger (Barennes et al., 1995: Transactions, 89,418) and Mali, Cameroun, C&e d’Ivoire and Burkina Faso (H. Barennes, personal communica- _ tion).

There must be more studies of rectal delivery and drugs formulated for this route, especially for children

‘Address for correspondence: Dr H. V. Wyatt, c/o 1 Hollyshaw *Terrace, Leeds, LS15 7BG, UK; fax +44 (0) 113 242 2042.

See p.719 for a review of this book, published in UK by Vi- rago Press (1995).