5 key points on fever in international travellers (clinical problem)

• a travel history should be obtained from anyone with a febrile illness
• malaria should be excluded in anyone with a fever who has been in a malaria-endemic area recently
• then consider dengue & other arbovirus infections if there has been mosquito exposure
• do not forget the neglected bacterial tropical infections: enteric fever, leptospirosis, scrub typhus & melioidosis
• do not forget to ask about potential risk for sexually-transmitted infections & HIV/AIDS

Trop Med revision in a day? Who said it can’t be done.

Oxford Handbook of Tropical Medicine, 3rd edn

Here are some on-line resources to assist you:

1. Expedition medicine
2. Malaria
3. Fever in an international traveller
4. Arbovirus infections
5. Diarrhoeal disease
6. Enteric fever
7. Neglected bacterial diseases
8. Pneumonia
9. Snake bite
10. Envenomation
11. Leishmaniasis

Self assessment questions:

Clinical scenarios

Key information sources:

• WHO neglected tropical diseases
• CDC Yellow Book on travel health
• Oxford Handbook of Tropical Medicine
• Manson’s Tropical Diseases

Another nasty mosquito-borne disease brought by the Indo-Papuan conveyor. S Richie, Cairns, QLD

[notes on a lecture at the Centenary of tropical medicine meeting, Townsville, QLD, 12-13th June, 2010]

In 1995 cases of fatal encephalitis appeared for the first time in the Torres Strait. These were initially thought to be Murray Valley Encephalitis, but on further investigation turned out to be Japanese encephalitis. Conditions in the Torres Strait Islands (TSI) were suitable for JE transmission due to the presence of wading birds, pigs and receptive mosquito vectors, notably Culex annulirostris. There was concern that the combination of herons, egrets and feral pigs might lead to the spread of JE south through much of the Eastern Australia.

By April 2005 Aedes albopictus was present in the TSI and both Dengue and Chikungunya viruses could be detected. Some of the movement of this mosquito vector was blamed on the movement of heavy mining equipment around the region. Expansion of its geographic distribution now included areas as far afield as SE USA, S Europe and the W Pacific. As a potential Dengue virus vector there was concern that it might spread into Eastern Australia. Its ability to breed easily in small quantities of still water included in the TSI beached boats and discarded coconut shells.

Much of the fauna of the regional has been divided into distinct biogeographic regions separated by the Wallace line (named after the naturalist and co-discoverer of natural selection, Alfred Russell Wallace). This neat separation of fauna and flora has been blurred recently by anthropogenic factors such as transmigration. There have also been climate-mediated effects such as the Indo-Pacific region drought caused by a pronounced El niño effect in 1997/8. Modelling of the movement of an air packet during Cyclone Sid showed the plausibility of propulsion of Cu annulirostris from Papua New Guinea to the northern Cape York Peninsula during a cyclone.

Further mosquito breeding opportunities have been created by the well-intentioned installation of rain water tanks in the TSI by aid agencies. The legal entitlement to permit traditional owners’ family visits adds another means of assisting arbovirus migration. So a cordon sanitaire was established against Aedes albopictus. Other Culicine species have been observed on the Australian mainland, including Culex gelidus close to Brisbane airport. This species is a potential vector of JE in SE Asia.

The mechanism of arbovirus movement from SE Asia to Australia is less a conduit and more a conveyor belt. The question is which arbovirus will be next? Could it be Chikungunya virus? And what impact will the global movement of the human population have on this process?

Make no mistake about it: our battle is with the germs. The front line is particularly volatile and liable to change in the immediate future. Here is an approximate view of the forces of infection ranged against us, subject to change on the arrival of more up to date disease intelligence.

The symbol conventions used follow the principles of campaign maps. You can see how thinly dispersed health units are in the northwest, compared to the disposition of immediate disease threats.

Those threats include arbovirus infections and neglected bacterial diseases, which you can follow on the Priobe Net and Life in the Fast Lane. Whitmore’s bacillus is particularly notable for its ability to lay low for many months and resurface when the conditions are right, to produce severe illness or less acute infection in pockets of disease activity throughout the Kimberley.  Leazar’s personal infection is unknown in this region, but other flavi-, alpha- and assorted other arboviruses are a potential mosquito-borne threat. The build-up of an unprotected civilian population in this region presents a possible vulnerability to the endemic infections of the area. Forewarned is forearmed.

Manson’s Tropical Diseases. 22nd edn. Ed GC Cook, AI Zumla. Elsevier, 2009. ISBN 978-1-4160-4470-0

When a medical textbook reaches its 22nd edition, it has clearly become an institution. Manson’s Tropical Diseases has become one of the leading sources of authoritative opinion on tropical medicine in the English-speaking world. The most recent edition goes well beyond the standard fare of tropical infectious diseases to cover the challenges of other medical specialties in the tropics and a collection of non-infective conditions. This diverse range of topics has been presented to a consistently high standard; a notable editorial achievement for a topic with such breadth. 89 chapters are divided into 12 sections and supplemented by on-line material in a series of 5 appendices. It adds up to 1783 pages of carefully crafted professional writing.

From recent use [FACTM on-line modules; Malaria & Arbovirus Infections] I have been particularly impressed by Nick White’s magisterial chapter on malaria and David Smith’s group’s review of arbovirus infections. Both chapters are examples of lucid prose that is a pleasure to read for reading’s sake. They are also one of reasons Manson’s Tropical Diseases has sustained its success over so many editions, through making the familiar read as new while making the genuinely novel accessible to a wider audience. The editors have achieved this difficult balancing act by retaining many of their chapter authors from the 21st edition.

Manson’s Tropical Diseases is recommended further reading for the FACTM pt 1 exam.

Sections: underlying factors in tropical medicine, symptoms and signs, system-oriented disease, related specialties in the tropics, environmental/genetic disorders, viral infection, rickettsial infections, bacterial infections, mycotic infections, protozoan infections, helminthic infections, ectoparasites.

The satirist, Jonathan Swift (1667-1745) wrote in 1733 that “Hobbes clearly proves, that every creature lives in a state of war by nature.” While the arboviruses and their mosquito vectors can hardly be described as leviathans, they continue to have an impact on the health of many millions living in the tropics.

The Arbovirus Infections unit for FACTM pt 1 study is now complete. Lecture notes for both modules (FACTM Arbo 1, and FACTM Arbo 2) can be found via this site. The live version takes place in the Emergency Department seminar room, Sir Charles Gairdner Hospital,  at 06:50hr next Tuesday (11th May, 2010). Further details on the Calendar function of this site (right hand contents bar). Sources of supplementary information on arbovirus infections can be found on the Priobe Net.