Onset of clinical immunity to Plasmodium falciparum among Javanese migrants to Indonesian Papua.

Onset of clinical immunity to Plasmodium falciparum occurred among Javanese migrants to Indonesian Papua. Surveillance of the 243 migrants investigated began on the day of their arrival in Indonesian Papua and continued for 33 months. Asexual parasitaemia without fever constituted objective evidence of clinical immunity. Compared with first infection, the odds ratio (OR) for not having fever at the fourth infection within 24 months was 3.2 [95% confidence interval (CI)=1.03-10.2; P=0.02]. The corresponding OR with fewer infections within 24 months was not distinguishable from 1.0. The level of the fourth parasitaemia within 24 months (N=58) was classified as 'high' or 'low' in relation to the median count at first infection (840 parasites/microl; N=187). Fourth parasitaemias that were low-but not those that were high (OR=1.8; CI=0.6-5.4; P=0.35)-were associated with dramatic protection from fever (OR=31; CI=3.5-1348; P=0.0001). Among the adult subjects, the risk of fever with low parasitaemia was significantly higher at the first infection than at the fourth (OR=12.6; CI=1.7-530; P=0.005), indicating the development of clinical immunity. A similar but less marked pattern appeared among the children investigated (OR=6.5; CI=0.8-285; P=0.06).

Malaria in a cohort of Javanese migrants to Indonesian Papua.

The epidemiology of infection by Plasmodium falciparum and P. vivax was investigated among Javanese migrants to an endemic region of Papua, Indonesia. A cohort of 243 migrants from Java was followed for malaria in a new settlement village in the endemic Armopa area of north-eastern Papua, beginning on the day each migrant arrived in the village. The subjects were monitored during home visits (three/week) and by the twice-monthly production of bloodsmears that were checked for malarial parasites. At the end of 33 months, 159 (65%) of the subjects remained under follow-up. The prevalence of parasitaemia in the village declined from 16% among those already living there when the study began in August 1996, to 5% when the study finished in June 1999. Over this period, 596 infections by P. falciparum and 723 by P. vivax occurred in the cohort, 22 and 27 of the subjects each experiencing at least six infections by P. falciparum and P. vivax, respectively. The incidence of malarial infection was higher during the first and second years post-migration (3.2 and 2.7 infections/person-year) than during the third (1.2 infections/person-year). Although the geometric mean parasite counts for P. falciparum increased over time (1209, 1478, and 1830 parasites/microl in the first, second and third years, respectively), the corresponding values for P. vivax (497, 535 and 490 parasites/microl) showed no such trend. Only one of the nine subjects who developed severe malaria (requiring intravenous quinine therapy) was a child, giving an odds ratio for a case of severe malaria being in an adult of 6.1 (P=0.08).

Primary infection by Plasmodium falciparum or P. vivax in a cohort of Javanese migrants to Indonesian Papua.

The clinical and parasitological characteristics of the first naturally acquired malarial infection have rarely been documented in humans. When 243 migrants from non-endemic Java were followed from the day of their arrival in Indonesian Papua, 217 (89%) were found to become infected with Plasmodium falciparum and/or P. vivax before they were lost to follow-up. The incidence of malarial infection in the children investigated (who were aged 6-10 years) was indistinguishable from that in the adults (aged >20 years), with 1.10 and 1.14 P. falciparum infections/person-year (relative risk=0.97; 95% confidence interval=0.72-1.29) and 1.47 and 1.49 P. vivax infections/person-year (relative risk=0.99; 95% confidence interval=0.72-1.29), respectively. During their first infections, the children had higher P. falciparum parasitaemias than the adults (with geometric means of 1318 and 759 parasites/microl, respectively; P=0.04) but similar P. vivax parasitaemias (with geometric means of 355 and 331 parasites/microl, respectively; P=0.76). At first infection, 56% of the subjects were febrile and 90% complained of symptoms. There were no differences between children and adults with respect to these two parameters, either for P. falciparum or P. vivax. These findings indicate that, with promptly diagnosed and treated uncomplicated malaria, migrant children and adults in north-eastern Indonesian Papua have an equal risk of malarial infection and of disease following their first infections with P. falciparum and P. vivax.

The drug sensitivity and transmission dynamics of human malaria on Nias Island, North Sumatra, Indonesia.

Nias Island, off the north-western coast of Sumatra, Indonesia, was one of the first locations in which chloroquine-resistant Plasmodium vivax malaria was reported. This resistance is of particular concern because its ancient megalithic culture and the outstanding surfing conditions make the island a popular tourist destination. International travel to and from the island could rapidly spread chloroquine-resistant strains of P. vivax across the planet. The threat posed by such strains, locally and internationally, has led to the routine and periodic re-assessment of the efficacy of antimalarial drugs and transmission potential on the island. Active case detection identified malaria in 124 (17%) of 710 local residents whereas passive case detection, at the central health clinic, confirmed malaria in 77 (44%) of 173 cases of presumed 'clinical malaria'. Informed consenting volunteers who had malarial parasitaemias were treated, according to the Indonesian Ministry of Health's recommendations, with sulfadoxine-pyrimethamine (SP) on day 0 (for P. falciparum) or with chloroquine (CQ) on days 0, 1 and 2 (for P. vivax). Each volunteer was then monitored for clinical and parasite response until day 28. Recurrent parasitaemia by day 28 treatment was seen in 29 (83%) of the 35 P. falciparum cases given SP (14, 11 and four cases showing RI, RII and RIII resistance, respectively). Recurrent parasitaemia was also observed, between day 11 and day 21, in six (21%) of the 28 P. vivax cases given CQ. Although the results of quantitative analysis confirmed only low prevalences of CQ-resistant P. vivax malaria, the prevalence of SP resistance among the P. falciparum cases was among the highest seen in Indonesia. When the parasites present in the volunteers with P. falciparum infections were genotyped, mutations associated with pyrimethamine resistance were found at high frequency in the dhfr gene but there was no evidence of selection for sulfadoxine resistance in the dhps gene. Night-biting mosquitoes were surveyed by human landing collections and tested for sporozoite infection. Among the five species of human-biting anophelines collected, Anopheles sundaicus was dominant (68%) and the only species found to be infective--two (1.2%) of 167 females being found carrying P. vivax sporozoites. The risk of malarial infection for humans on Nias was considered high because of the abundance of asymptomatic carriers, the reduced effectiveness of the available antimalarial drugs, and the biting and infection 'rates' of the local An. sundaicus.

Randomized, parallel placebo-controlled trial of primaquine for malaria prophylaxis in Papua, Indonesia.

Malaria causes illness or death in unprotected travelers. Primaquine prevents malaria by attacking liver-stage parasites, a property distinguishing it from most chemoprophylactics and obviating 4-week postexposure dosing. A daily adult regimen of 30 mg primaquine prevented malaria caused by Plasmodium falciparum and P. vivax for 20 weeks in 95 of 97 glucose-6-phosphate dehydrogenase (G6PD)-normal Javanese transmigrants in Papua, Indonesia. In comparison, 37 of 149 subjects taking placebo in a parallel trial became parasitemic. The protective efficacy of primaquine against malaria was 93% (95% confidence interval [CI] 71%-98%); against P. falciparum it was 88% (95% CI 48%-97%), and >92% for P. vivax (95% CI >37%-99%). Primaquine was as well tolerated as placebo. Mild methemoglobinemia (mean of 3.4%) returned to normal within 2 weeks. Blood chemistry and hematological parameters revealed no evidence of toxicity. Good safety, tolerance, and efficacy, along with key advantages in dosing requirements, make primaquine an excellent drug for preventing malaria in nonpregnant, G6PD-normal travelers.

The T76 mutation in the pfcrt gene of Plasmodium falciparum and clinical chloroquine resistance phenotypes in Papua, Indonesia.

The T76 mutation in the pfcrt gene has been linked to chloroquine (CQ) resistance in Plasmodium falciparum. PCR-based analysis of pfcrt alleles was performed on pre-treatment samples from 107 individuals who had P. falciparum infections and lived in Papua, Indonesia. The results of a 28-day, in-vivo test revealed clinical resistance to CQ in 79 (74%) of the samples. The crude sensitivity of the pfcrt T76 assay for detecting the CQ-resistant infections in the samples was 96% and the crude specificity 52%. Discordance between pfcrt genotype and in-vivo phenotype was analysed either by genotyping of the merozoite surface protein-2 (to distinguish re-infection from recrudescence) or by amplification of the P. falciparum-specific small-subunit ribosomal RNA (ssrRNA) gene, using nested PCR (to detect any sub-patent but resistant parasites in infections misclassified as sensitive by the in-vivo test). When adjusting for the results of these analyses, the sensitivity and specificity of the pfcrt T76 assay for detecting the CQ-resistant infections became 93% and 82%, respectively. Overall, the present results indicate that the pfcrt T76 assay may be used to forecast therapeutic failure caused by CQ resistance. Validation requires exploration of the phenotype classifications based on the results of in-vivo tests, using genetic analyses that distinguish re-infection from recrudescence and detect microscopically subpatent parasitaemias.

Incidence of symptomatic and asymptomatic Plasmodium falciparum infection following curative therapy in adult residents of northern Ghana.

Adult residents of holoendemic malaria regions in Africa have a naturally acquired immunity (NAI) to malaria that renders them more resistant to new infections, limits parasitemia, and reduces the frequency and severity of illness. Given such attributes, it is not clear how one might evaluate drug or vaccine efficacy in adults without serious confounding. To determine symptomatic and asymptomatic malaria attack rates in adults of northern Ghana, 197 men and women underwent curative therapy for any pre-existing malaria infections at the start of the high transmission (wet) season. They were monitored for first parasitemia and first clinical episode of infection by Plasmodium falciparum over a 20-week period (May-October 1996). The cumulative incidence of primary infection by P. falciparum was 0.98 and incidence density of infection was calculated to be 7.0 cases/person-year. Symptoms were reported by 19.5% of the individuals at the time of first recurrent parasitemia. Incidence of infection, parasite density, and the frequency of symptoms were comparable in males and females. The results suggest that NAI did not provide these adults with significant defense against rapid re-infection and suggest that this population-infection design could serve to demonstrate the efficacy of a drug or vaccine in preventing parasitemia.

Evidence for different mechanisms of chloroquine resistance in 2 Plasmodium species that cause human malaria.

Chloroquine (CQ)-resistant Plasmodium vivax malaria was first reported 12 years ago, nearly 30 years after the recognition of CQ-resistant P. falciparum. Loss of CQ efficacy now poses a severe problem for the prevention and treatment of both diseases. Mutations in a digestive vacuole protein encoded by a 13-exon gene, pfcrt, were shown recently to have a central role in the CQ resistance (CQR) of P. falciparum. Whether mutations in pfcrt orthologues of other Plasmodium species are involved in CQR remains an open question. This report describes pfcrt homologues from P. vivax, P. knowlesi, P. berghei, and Dictyostelium discoideum. Synteny between the P. falciparum and P. vivax genes is demonstrated. However, a survey of patient isolates and monkey-adapted lines has shown no association between in vivo CQR and codon mutations in the P. vivax gene. This is evidence that the molecular events underlying P. vivax CQR differ from those in P. falciparum.

Mutations in the pfmdr1, dhfr and dhps genes of Plasmodium falciparum are associated with in-vivo drug resistance in West Papua, Indonesia.

This study (conducted in 1996-99) examines the association of mutations in pfmdr1, dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes of Plasmodium falciparum with in-vivo drug resistance in West Papua, Indonesia. Initially, 85 patients infected with P. falciparum were treated with chloroquine, of whom 21 were cleared of parasites, 49 had parasitaemias classified as RI, RII or RIII resistance and 1 patient had recrudescent parasitaemia. Fansidar (pyrimethamine-sulfadoxine) was the second-line treatment and 18 patients were cleared of parasites and 31 had continuing infections classified as RI, RII or RIII resistance and 1 patient had recrudescent parasitaemia. The pfmdr1, dhfr and dhps genes were examined for mutations previously shown to be associated with resistance to these drugs. In this study, mutations in pfmdr1 were associated with chloroquine resistance and mutations in both dhfr and dhps were associated with Fansidar resistance in vivo. Interestingly, Gly-437 in dhps along with Arg-59/Asn-108 in dhfr were associated with RI, RII and RIII resistance whereas Glu-540 was highly associated with only RII and RIII Fansidar resistance. This finding supports the hypothesis that the molecular basis of RI, RII and RIII Fansidar resistance involves an accumulation of mutations in both dhfr and dhps. These results suggest that mutations in both dhfr and dhps genes are a good predictor of potential Fansidar treatment failure.

Adaptation of a chloroquine-resistant strain of Plasmodium vivax from Indonesia to New World monkeys.

The spread of chloroquine-resistant Plasmodium vivax from Papua New Guinea and Indonesia poses a serious health threat to areas of Southeast Asia where this species of malaria parasite is endemic. A strain of P. vivax from Indonesia was adapted to develop in splenectomized Aotus lemurinus griseimembra, Aotus vociferans, Aotus nancymai, and Saimiri boliviensis monkeys. Transmission to splenectomized Saimiri monkeys was obtained via sporozoites. Chemotherapeutic studies indicated that the strain was resistant to chloroquine and amodiaquine while sensitive to mefloquine. Infections of chloroquine-resistant P.vivax in New World monkeys should be useful for the development of alternative treatments.

Effects of permethrin on the salivary glands and neuroendocrine organs of unfed female Hyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae).

Permethrin-impregnated fabric has been shown to be an effective repellent against various tick species. However, some tick species are not repelled by this chemical. In Hyalomma dromedarii (Koch), permethrin exposure is reported to actually enhance the tick's attachment behavior. This study evaluated the histological effects of permethrin exposure on the salivary glands and neuroendocrine organs of unfed, virgin H. dromedarii ticks of uniform age. Three fabric treatments consisting of unwashed-untreated (control), washed after treatment (0.125 mg [AI] / cm2) and unwashed-treated were used after 5- and 10-min exposure times for unfed, unmated females. For all of the organs examined, the cellular structure of treated ticks differed from controls as evidenced by increases in cellular activity, as well as significant increases in the size of the cells of the organs under study (P < 0.05). These data conclusively demonstrate that an unexpected enhanced attachment response observed in this tick species after permethrin exposure is the direct result of increased neurosecretory and salivary gland activity induced by that exposure.

Performance of the OptiMAL assay for detection and identification of malaria infections in asymptomatic residents of Irian Jaya, Indonesia.

The OptiMAL assay, a new immunochromatographic "dipstick" test for malaria based on detection of Plasmodium lactate dehydrogenase (pLDH), is purported to detect infections of approximately 200 parasites/microL of blood and to differentiate between Plasmodium falciparum and non-P. falciparum. We evaluated OptiMAL performance by comparing the test strip interpretations of two independent readers with consensus results obtained independently by expert malaria microscopists. Unbiased measures of sensitivity were derived by applying the OptiMAL test for detection and differentiation of light, asymptomatic infections by P. falciparum and Plasmodium vivax. OptiMAL readings were separated in time to determine whether the reaction signal was stable. Microscopy identified infections in 225 of 505 individuals screened; those with P. falciparum (n = 170) averaged 354 asexual forms/microL and P. vivax/Plasmodium malariae (n = 112) averaged 216 asexual forms/microL of blood. Concordance between OptiMAL and microscopy was 81% and 78% by the two independent readings. The assay's sensitivity for detection of any malaria species was 60.4% and 70.2% respectively and specificity was 97% and 89%. Most cases identified by microscopy as P. falciparum were graded as negative or non-falciparum by both OptiMAL readers. OptiMAL false negatives as well as misidentifications were related to low parasitemias (< 500/microL). The OptiMAL assay demonstrated 88-92% sensitivity for detecting infections of 500-1,000 parasites/microL, a range covering the mean parasitemia of primary symptomatic P. falciparum infections in malaria-naïve Indonesian transmigrants. This device was markedly less sensitive than expert microscopy for discriminating between malaria species and is presently unsuited for use as an epidemiological screening tool. The OptiMAL assay is not approved for diagnostic use but is commercially available for research purposes only.

Assessing drug sensitivity of Plasmodium vivax to halofantrine or choroquine in southern, central Vietnam using an extended 28-day in vivo test and polymerase chain reaction genotyping.

Chloroquine-resistant Plasmodium vivax malaria is emerging in Oceania, Asia, and Latin America. We assessed the drug sensitivity of P. vivax to chloroquine or halofantrine in two villages in southern, central Vietnam. This area has chloroquine-resistant Plasmodium falciparum but no documented chloroquine-resistant P. vivax. Standard dose chloroquine (25 mg/kg, over 48 hours) or halofantrine (8 mg/kg, 3 doses) was administered to 29 and 25 patients, respectively. End points were parasite sensitivity or resistance determined at 28 days. Of the evaluable patients, 23/23 100% (95% confidence interval [CI] 85.1-100) chloroquine and 21/24 (87.5%) (95% CI 67.6-97.3) halofantrine-treated patients were sensitive. Three halofantrine recipients had initial clearance but subsequent recurrence of their parasitemias. Genotyping of the recurrent and Day 0 parasitemias differed, suggesting either new infections or relapses of liver hypnozoites from antecedent infections. Among these Vietnamese patients, P. vivax was sensitive to chloroquine and halofantrine. Genotyping was useful for differentiating the recurrent vivax parasitemias.

Enzyme polymorphism and genetic variability of laboratory populations of Phlebotomus papatasi, P. bergeroti, P. langeroni, and P. perniciosus.

Enzyme allomorph frequency and electrophoretic mobility were evaluated to clearly separate between morphologically similar sandfly species and to yield quantitative measures of their genetic similarity. Twelve enzyme systems were studied in laboratory colonies of Phlebotomus perniciosus, P. langeroni, P. papatasi, and P. bergeroti. Phlebotomus perniciosus and P. langeroni confirmed vectors of visceral leishmaniasis, were found to have fixed diagnostic allomorph differences at 3 enzyme loci (ICD-2, FUM, XDH). Phlebotomus papatasi, a known vector of cutaneous leishmaniasis and phleboviruses and P. bergeroti, a newly colonized suspected vector, were clearly differentiated from each other by a fixed allomorph at the MPI locus. Polymorphism at loci in these sandfly colonies ranged from 6.7% (P. perniciosus) to 43.7% (P. papatasi), with lowest levels seen in the older colonies. Expected heterozygosity was highest in P. papatasi, despite 33 generations of inbreeding, and comparable to that of P. bergeroti in its 7th generation. Against a scale of 0 for completely different, and 1.0 for identical genotypes, the enzyme data yielded indices of genetic identity (I) between P. perniciosus and P. langeroni and between P. papatasi and P. bergeroti of 0.783 and 0.737, respectively. These relatively high levels of genetic identity, paralleling similarities between species in morphology, inbreeding compatibility, and vectorial attributes, provide evidence of comparable and recent evolutionary divergence.

Plasmodium falciparum mdr1 mutations and in vivo chloroquine resistance in Indonesia.

Mutations in the Pfmdr1 gene are reported to be associated with chloroquine resistance in some Plasmodium falciparum isolates. A polymerase chain reaction/restriction fragment length polymorphism method was used for the detection of Pfmdr1 mutations in chloroquine-resistant field isolates of P. falciparum collected in Irian Jaya. The frequency of Pfmdr1 mutations was significantly higher in chloroquine-resistant P. falciparum parasites than background frequencies observed in the same location. The 7G8 mutation was identified in some parasites although always in a mixed genotype status. Chloroquine-resistant P. falciparum specimens were characterized using the World Health Organization 28-day criteria, supplemented by demonstrating adequate chloroquine absorption and genetic analysis.

Cyclospora cayetanensis among expatriate and indigenous populations of West Java, Indonesia.

From January 1995 through July 1998, we investigated the occurrence of Cyclospora cayetanensis infection associated with gastrointestinal illness or diarrhea in foreign residents and natives of West Java, Indonesia. We found that C. cayetanensis was the main protozoal cause of gastrointestinal illness and diarrhea in adult foreign residents during the wet season. The parasite rarely caused illness in the indigenous population or in children.

In vivo responses to antimalarials by Plasmodium falciparum and Plasmodium vivax from isolated Gag Island off northwest Irian Jaya, Indonesia.

There is renewed interest in the rich nickel and cobalt deposits of Pulau Gag, an isolated but malarious island off the northwest coast of Irian Jaya. In preparation for an expanded workforce, an environmental assessment of malaria risk was made, focusing upon malaria prevalence in the small indigenous population, and the in vivo sensitivity of Plasmodium falciparum and P. vivax to chloroquine (CQ) and sulfadoxine/pyrimethamine (S/P), the respective first- and second-line drugs for uncomplicated malaria in Indonesia. During April-June 1997, mildly symptomatic or asymptomatic malaria infections were found in 24% of 456 native residents. Infections by P. falciparum accounted for 60% of the cases. Respective day 28 cure rates for CQ (10 mg base/kg on days 0 and 1; 5 mg/kg on day 2) in children and adults were 14% and 55% (P < 0.005). Type RII and RIII resistance characterized only 5% of the CQ failures. Re-treatment of 36 P. falciparum CQ treatment failures with S/P (25 mg/kg and 1.25 mg/kg, respectively) demonstrated rapid clearance and complete sensitivity during the 28-day follow-up period. More than 97% of the P. vivax malaria cases treated with CQ cleared parasitemia within 48 hr. Three cases of P. vivax malaria recurred between days 21 and 28, but against low drug levels in the blood. The low frequency of RII and RIII P. falciparum resistance to CQ, the complete sensitivity of this species to S/P, and the absence of CQ resistance by P. vivax are in contrast to in vivo and in vitro test results from sites on mainland Irian Jaya.

Lymphocyte response to tetanus toxin T-cell epitopes: effects of tetanus vaccination and concurrent malaria prophylaxis.

Synthesized T-cell epitopes of tetanus toxin are universally immunogenic and serve to enhance immune response when they are used as vaccine carriers of B-cell epitopes. The immunogenicity of the P2, P30, and P2P30 T-cell epitopes of tetanus toxin and whole tetanus toxoid (TT) was evaluated by in vitro proliferation assay of lymphocytes from men with no history of tetanus vaccination who were enrolled in a malaria prophylaxis trial. The enhancement of immune response by tetanus vaccination (Td) and possible antagonism by the antimalarial drugs, was measured by pre- and post-Td comparisons within and between immunized prophylaxis groups (primaquine, chloroquine, placebo) and a nonimmunized control group. Constructs demonstrated low immunogenicity relative to TT in all groups. Relative to both control and its own baseline, the immunized primaquine prophylaxis group was distinct in demonstrating significantly increased proliferation against all three subunits and at both high (30 microg ml(-1)) and low (3 microg ml(-1)) concentrations. Immunization elicited significantly increased proliferation responses by placebo and chloroquine prophylaxis groups against only the P2P30 construct. Despite these significant post-Td changes, a low concentration of TT 0.1 microg ml(-1)) stimulated proliferation 7-10 times over that induced by the greatest concentration of the constructs.

Malaria prophylaxis using azithromycin: a double-blind, placebo-controlled trial in Irian Jaya, Indonesia.

New drugs are needed for preventing drug-resistant Plasmodium falciparum malaria. The prophylactic efficacy of azithromycin against P. falciparum in malaria-immune Kenyans was 83%. We conducted a double-blind, placebo-controlled trial to determine the prophylactic efficacy of azithromycin against multidrug-resistant P. falciparum malaria and chloroquine-resistant Plasmodium vivax malaria in Indonesian adults with limited immunity. After radical cure therapy, 300 randomized subjects received azithromycin (148 subjects, 750-mg loading dose followed by 250 mg/d), placebo (77), or doxycycline (75, 100 mg/d). The end point was slide-proven parasitemia. There were 58 P. falciparum and 29 P. vivax prophylaxis failures over 20 weeks. Using incidence rates, the protective efficacy of azithromycin relative to placebo was 71.6% (95% confidence interval [CI], 50.3-83.8) against P. falciparum malaria and 98.9% (95% CI, 93.1-99.9) against P. vivax malaria. Corresponding figures for doxycycline were 96.3% (95% CI, 85.4-99.6) and 98% (95% CI, 88.0-99.9), respectively. Daily azithromycin offered excellent protection against P. vivax malaria but modest protection against P. falciparum malaria.

Norwalk-like virus and bacterial pathogens associated with cases of gastroenteritis onboard a US Navy ship.

Acute gastroenteritis is a potential cause of substantial morbidity in U.S. military personnel during deployment. This study investigated the microbial causes of diarrhea in U.S. troops on exercises in Southeast Asia aboard the U.S.S. Germantown from March through May 1996. A total of 49 (7%) patients with diarrhea reported to sick call during a 3-month deployment involving 721 personnel. Diarrheal samples from 49 patients were subjected to bacterial and parasitologic examination, but sufficient samples from only 47 of 49 were available for analysis of the presence of Norwalk-like virus (NLV). Of the 49 diarrhea cases, 10 (20.4%) appeared to be due to bacterial etiology alone, 10 (20.4%) due to bacteria and the prototype Taunton agent (TNA), 11 (22.4%) due to TNA only, and 4 (8.0%) due to parasites. Norwalk-like virus RNA was present in 21 (45%) of 47 stool samples from the diarrhea cases, 10 with bacterial etiologies and 11 without bacterial or parasitic etiologies. No pathogen was detected in 14 (29%) of the cases. Four of the controls showed the presence of parasitic organisms. Of the 11 cases in which enterotoxigenic Escherichia coli was isolated, 8 were positive for colonization factor antigen (CFA/IV), and 3 were CFA-negative. The bacterial pathogens tested were all susceptible to gentamicin, and furadantin, but were resistant to ceftriaxone and norfloxacin, including 75% of the Campylobacter spp. These data support the view that the major cause of diarrhea for troops deployed in this geographic area is most likely NLVs.