eMJA: Kitchener et al, Malaria in the Australian Defence Force during and after participation in the International Force in East Timor (INTERFET)

Responding to Crisis

Malaria in the Australian Defence Force during and after participation in the International Force in East Timor (INTERFET)

Scott J Kitchener, Alyson M Auliff and Karl H Rieckmann

Malaria in Australian Defence Force members has been far more common in East Timor than in other recent overseas deployments. By six months after all 5500 members of the International Force in East Timor had returned to Australia, 267 malaria infections had been reported to the Army Malaria Institute. Only 64 of those affected had their first clinical episode during their 4-5 months in East Timor, and about two-thirds of these infections were caused by Plasmodium falciparum. The remaining 212 soldiers developed their first symptoms after returning to Australia, and all but two infections were caused by P. vivax. After treatment, 44 soldiers had relapses of their vivax infections; 11 had a second relapse and two had a third relapse. These findings raise several issues about prevention and management of malaria in the ADF.

MJA 2000; 173: 583-585

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Antimalarial measures - High malaria rates in two battalions - Notification of malaria infections - Malaria infections with onset in East Timor - Malaria infections with onset in Australia - Parasite resistance to drugs? - References - Authors' details
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On 12 September 1999, President Habibie of Indonesia invited an international peace-keeping force to help restore peace in East Timor after significant civil unrest. The United Nations Security Council Recommendation 1264 (15 September 1999) directed the formation of an International Force in East Timor (INTERFET). On 20 September, lead elements of INTERFET from the Australian Defence Force (ADF) landed in Dili and were soon followed by approximately 5500 ADF personnel assigned to serve in different parts of East Timor. INTERFET concluded on 23 February 2000, when most ADF personnel came under the command of the Peace Keeping Force of the United Nations Transition Administration for East Timor (UNTAET).

Antimalarial measures

ADF personnel used various personal protection measures against mosquitoes, including insect repellents and permethrin-treated mosquito-nets. Preventive medicine units also carried out mosquito control measures. Personnel were given doxycycline (100 mg daily) for prophylaxis, starting one or two days before departure for East Timor and continuing for two weeks after return to Australia. Weekly doses of mefloquine (250 mg) were used as an alternative if doxycycline prophylaxis was not tolerated or contraindicated. In addition, terminal prophylaxis with primaquine (7.5 mg three times daily) was given for two weeks after return to Australia. In general, chemoprophylaxis was not taken under supervision.

High malaria rates in two battalions

On 23 October 1999 -- approximately one month after deployment -- the first malaria infection was diagnosed in a soldier serving with the Second Battalion, Royal Australian Regiment (2RAR). During the four months of the battalion's deployment on the northern border region, mainly during the wet season, 17 members of the battalion developed malaria (monthly rate, 0.71%). Most of these cases were traced to exposures in Batugade (see Box 1). The Third Battalion (3RAR), deployed to the Oecussi (Ambino) enclave for five months, reported 24 cases of malaria (monthly rate, 0.73%). These malaria attack rates were the highest observed during the ADF involvement in INTERFET. Based on data from ADF units deployed to other areas of East Timor, other high risk areas were the mouth of the Komoro River in Dili (near the international airport) and the southern border regions near Suai.

Within 7-8 months after returning to Australia, a further 127 soldiers from 2RAR and 3RAR had developed malaria. Combined with the 41 cases with onset overseas, this equates to nearly three (2.96) of every 100 soldiers from these two battalions acquiring malaria for every month's deployment to East Timor. This rate is higher than that experienced by Australian military forces deployed recently to Southeast Asia and Africa¹ and Bougainville (unpublished), but lower than that observed during some military deployments to Papua New Guinea.²

Notification of malaria infections

That malaria was a health problem was obvious during the five-month duration of INTERFET, and this became even more noticeable after the return of troops to Australia. Clinical episodes of malaria were reported to the Central Malaria Register of the ADF, which is managed by the Army Malaria Institute (AMI). The AMI records clinical and epidemiological data, and, whenever possible, confirms the diagnosis by microscopic examination of blood films or polymerase chain reaction (PCR).

Malaria infections with onset in East Timor

During deployment of the entire Australian contribution to INTERFET, 64 ADF members developed malaria while in East Timor (Box 2a). About two-thirds of these infections were caused by Plasmodium falciparum and the remainder by P. vivax. This 2:1 ratio reflects the relative prevalence of these two species in the local communities,³ and suggests that there was inadequate compliance with doxycycline prophylaxis or that there were other factors resulting in lower drug concentrations, such as drug deterioration under adverse environmental conditions or reduced bioavailability.

The falciparum infections were treated with either a one-day course of mefloquine, or quinine (3 days) combined with doxycycline (10 days). One patient tolerated mefloquine poorly and received atovaquone and proguanil (3 days). None of the patients had a recurrence of clinical symptoms and were presumably cured of their infections.

The vivax infections were treated with a combination of chloroquine (3 days) and primaquine (14 days). All affected patients responded well to treatment, but a few had a recurrence of clinical symptoms and parasitaemia (relapse) a few weeks to months later (Box 2b).

Malaria infections with onset in Australia

Many more malaria infections had their onset after soldiers had left East Timor, with the first clinical episode of malaria occurring in 212 ADF members after their return to Australia (Box 2a). They all had vivax malaria, except for two soldiers who developed falciparum malaria within two weeks of their return. This indicates that doxycycline prophylaxis effectively prevented the development of the blood stages of P. vivax, but that dormant parasites (hypnozoites) in the liver reactivated, entered the bloodstream, and initiated acute attacks of malaria after doxycycline prophylaxis was discontinued. Such initial episodes of vivax malaria could occur many months after return to Australia, with most ADF personnel involved in INTERFET leaving East Timor between December and March 2000 (Box 2b). A few more initial infections will undoubtedly emerge up to 12 months or longer after return from East Timor.

It was obvious that terminal prophylaxis with primaquine had not been successful in eradicating all the residual hepatic parasites. As primaquine is the only drug capable of eliminating such parasites, the 210 patients hospitalised with vivax malaria received primaquine again (22.5 mg or 30 mg daily) in addition to a standard course of chloroquine (3 days). Compliance with treatment courses was undoubtedly better than with terminal prophylaxis.

Forty-four soldiers had relapses 22-180 days (median, 77 days) after treatment. Although most soldiers were cured after a second course of chloroquine and primaquine, 11 had a second relapse 28 to 157 days (median, 82 days) after treatment and two had a third relapse 145 to 159 days after the third course of treatment. Apart from the distress caused by these recurrent acute episodes of malaria, the overall effect on operational capability was quite substantial. Clearly, there is an urgent need for more effective malaria prophylaxis.

Parasite resistance to drugs?

Doxycycline has proven to be very effective in the past for prophylaxis of both falciparum and vivax malaria. In combination with any rapid-acting drug, it also cures falciparum infections provided it is taken for 7-10 days. All the falciparum infections in East Timor were cured after treatment with doxycycline, indicating that the parasites had not developed resistance to doxycycline.

Primaquine tolerance is a well-recognised phenomenon in Papua New Guinea² and other Melanesian countries, but it has not been well documented in East Timor. The surprisingly large number of soldiers who developed vivax malaria after returning to Australia obviously had their infections suppressed effectively by doxycycline while they were in East Timor. Their delayed malaria attacks after their return were the result of either deteriorating drug compliance or primaquine-tolerant hepatic parasites. The fact that 44 (21%) of the 210 patients with vivax malaria had a relapse of their infections (a quarter on more than one occasion), under more closely supervised drug administration, indicates that primaquine-tolerant parasites are present in East Timor.

Efforts currently being made to reduce the many malaria casualties in East Timor are summarised in Box 3.

References

Shanks GD, Roessler P, Edstein MD, Rieckmann KH. Doxycycline for malaria prophylaxis in Australian soldiers deployed to United Nations Missions in Somalia and Cambodia. Milit Med 1995; 160: 443-445.
Rieckmann KH, Yeo AET, Davis DR, et al. Recent military experience with malaria chemoprophylaxis. Med J Aust 1993; 158: 446-449.
World Health Organization. East Timor epidemiological profile, September 1999 <http://www.who.ch/eha/> (accessed November 2000).

Authors' details

Army Malaria Institute, Gallipoli Barracks, QLD.
Scott J Kitchener, FAFPHM FACTM, Officer Commanding Clinical Field Section;
Alyson M Auliff, BSc(Hons), Scientific Officer, Clinical Field Section;
Karl H Rieckmann, MD, Director.

Reprints: Major S Kitchener, AMI, Gallipoli Barracks, Milpo, QLD 4152.
scott.kitchenerATdefence.gov.au

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