The American Journal of Tropical Medicine and Hygiene - Volume 69, Issue 1, July 2003

To determine the feasibility of using short-course zidovudine (ZDV) to prevent mother-to-child transmission of human immunodeficiency virus (HIV) in a breastfeeding population in a rural area in Kenya, pregnant mothers attending clinics in seven health centers in western Kenya between 1996 and 1998 were requested to volunteer for participation in this study. The HIV-infected mothers were given a daily dose of 400 mg of ZDV starting at 36 weeks of gestation and another 300 mg every three hours intrapartum. After delivery, mothers and their children were followed-up and clinically monitored every 3–4 months for two years, and child and mother mortality rates were analyzed. Of the 825 mothers who consented, 216 (26.2%) were infected with HIV. Of those infected, 51 (23.6%) took the full prescribed dose, 69 (31.9%) took only the prenatal dose, and the remaining 96 (44.4%) did not take any dose. Failure to take ZDV was attributed mainly to delivery occurring earlier than expected, while non-compliance to the intrapartum dose was due to mothers giving birth at home and fear of traditional birth attendants. By the end of the second year, 75 HIV-exposed children (34.7%) and 33 HIV-infected mothers (15.3%) had died. The HIV-free survival of children at 24 months was significantly associated with mother survival (P < 0.001) and prenatal ZDV compliance (P < 0.003). Our findings suggest that implementation of programs for prevention of mother-to-child transmission of HIV in rural areas of Africa need to consider the various socioeconomic and cultural barriers that may prevent successful uptake of antiretroviral prophylaxes. Similarly, the rapid disease progression in mothers may eliminate the increase in child survival due to ZDV prophylaxis.

We studied prospectively 801 Thai patients admitted to the Bangkok Hospital for Tropical Diseases with acute, symptomatic Plasmodium vivax malaria to determine the optimum duration of treatment with oral artesunate and the safety, tolerability, and effectiveness of a high dose of primaquine in prevention of relapse. Patients were randomly assigned to one of four treatment groups: 1) a five-day course of artesunate (Group A5); 2) a seven-day course of artesunate (Group A7); 3) a five-day course of artesunate plus a 14-day course of high-dose primaquine (0.6 mg/kg, maximum dose = 30 mg) (Group A5 + P); and 4) a seven-day course of artesunate plus a 14-day course of high-dose primaquine (Group A7 + P). During 28 days of observation, P. vivax reappeared in the blood of 50% of those who received artesunate alone (Groups A5 and A7), compared with none of those who received primaquine (Groups A5 + P and A7 + P; P < 0.0001). Adverse effects were confined to the 13 patients with a deficiency for glucose-6-phosphate dehydrogenase; high-dose primaquine (0.6 mg/kg of base a day) had to be stopped in four (31%) patients because of a significant decrease in the hematocrit. The combination of five days of artesunate and 14 days of primaquine is a highly effective and generally well-tolerated treatment regimen for vivax malaria in Thailand.

In a randomized controlled trial, chloroquine monotherapy was compared with the combination of artesunate and chloroquine for treating uncomplicated Plasmodium falciparum malaria in 536 Gambian children. Chloroquine-treated children exhibited a 28-day clinical failure rate of 15% (95% confidence interval [CI] = 9.2–22%) compared with 11% (7.8–15%) among children receiving the combination (P = 0.08, by Wilcoxon test). Seventy-three percent of chloroquine-treated children exhibited parasitemia during follow-up compared with 49% of children receiving the combination (relative risk = 1.5, 95% CI = 1.3–1.7; χ2 = 21.18, P < 0.001). A significant reduction in clinical and parasitologic treatment failure in the combination group occurred in the first two weeks following treatment, but this was eroded over weeks three and four of follow-up. The impact of combination therapy on the transmission of chloroquine-resistant parasites is discussed. Chloroquine plus artesunate is not sufficiently efficacious to justify its introduction as a replacement for chloroquine monotherapy in The Gambia.

The NOW® ICT Malaria P.f./P.v. for Whole Blood (Binax, Inc., Portland, ME) is a new malaria rapid diagnostic device that represents a technical advance over previous assays, such as ICT™ Malaria P.f./P.v. and ICT™ Malaria P.f.. We evaluated this device in March 2001 in symptomatic patients at malaria clinics in Maesod, Thailand. Microscopic examination of Giemsa-stained blood smears was the reference standard. In 246 patients, microscopy showed 32 (13.0%) infected with Plasmodium falciparum, 63 (25.6%) with P. vivax, 6 (2.4%) with mixed infections of P. falciparum and P. vivax, 5 (2.0%) with P. malariae, and 140 (56.9%) negative. Sensitivity for P. falciparum was 100% and specificity was 96.2% (200 of 208; 95% confidence interval [CI] = 92–98). For P. vivax, sensitivity was 87.3% (55 of 63; 95% CI = 77–93) and specificity was 97.7% (173 of 177; 95% CI = 95–99), but all the four false-positive results were microscopically positive for P. malariae; thus, specificity for non-falciparum Plasmodium was 100%. These results suggest improved performance over NOW® ICT predecessors.

Plasmodium falciparum malaria infection induces elevated blood levels of both total immunoglobulin and anti-plasmodial antibodies belonging to different isotypes. We have previously shown that donors living in areas of malaria transmission develop malaria-specific IgE antibodies that are present at highest concentrations in patients with severe disease, suggesting a role for this isotype in malaria pathogenesis. To establish the possible importance of IgE in the course and severity of this disease, we have analyzed a large and homogenous group of African children (age range = 6 months to 15 years) belonging to one ethnic group (Mossi) living in identical epidemiologic conditions in the same urban area (Ougadougo) of Burkina Faso. While IgG antibodies to P. falciparum increased to high concentrations in very young children and then remained at these levels in older patients, IgE antibodies increased with age, becoming most significantly elevated in children more than four years of age. In older children, those with severe malaria had significantly higher IgE antibody levels than those with non-severe disease. No significant differences between the patient groups were seen for IgG antibodies to P. falciparum. However, when the patients with severe malaria were divided into two groups distinguished by the presence of absence of coma, both IgG and IgE antibodies against malaria were lower in the comatous patients than in the non-comatous patients The results support the conclusion that IgE antibodies against malaria, regardless of their possible protectivity, also contribute to disease severity in this large and homogenous group of African children.

Immune responses directed at glycosylphosphatidylinositol (GPI) anchors of Plasmodium falciparum may offer protection against symptomatic malaria. To independently explore the effect of age on generation of the anti-GPI IgG response, we measured serum anti-GPI IgGs in a longitudinal cohort of migrant Javanese children (6–12 years old) and adults (≥20 years old) with equivalent numbers of exposures to P. falciparum in Papua, Indonesia. While the peak response in adults was achieved after a single infection, comparable responses in children required ≥3–4 infections. Significantly fewer children (16%) than adults (41%) showed a high (optical density > 0.44) anti-GPI IgG response (odds ratio [OR] = 3.8, 95% confidence interval [CI] = 2.3–6.3, P < 0.0001), and adults were more likely to show a persistently high response (OR = 5.5, 95% CI = 1.0–56.8, P = 0.03). However, the minority of children showing a strong response were significantly less likely to experience symptoms with subsequent parasitemia compared with those with a weak response (OR = 4.0, 95% CI = 1.1–13.8, P = 0.02). This effect was not seen among high- and low-responding adults (OR = 1.2, 95% CI = 0.5–2.8, P = 0.60). Host age, independent of cumulative exposure, apparently represents a key determinant of the quantitative and qualitative nature of the IgG response to P. falciparum GPI.

To evaluate the effect of long-term storage of sample filters on the sensitivity of polymerase chain reaction (PCR) detection of malaria, 252 blood spots from patients with microscopically confirmed Plasmodium falciparum malaria were analyzed and stratified by storage duration. The spots were collected between 1996 and 2000 on filter paper and stored at room temperature. A Chelex-based method was used to extract the DNA. Unexpectedly, after the first purification, the sensitivity of the PCR from recently stored samples was low and showed progressively increased with time storage (P = 0.003, by chi-square test for linear trend). This suggested that PCR inhibitors were easier to dissolve from the more recent blood spots (< 4 years old) than from blood spots ≥4 years old, thus leading to a time-dependent increase in PCR sensitivity. However, if DNA was purified again (when the first PCR result was negative), the cumulative sensitivity was not influenced by storage duration. This indicated that length of storage is not a critical issue providing purification is sufficient.

A cross-sectional study was conducted in the Peruvian Amazon to test the hypothesis that a reservoir of asymptomatic malaria parasitemic patients would form the basis for continuing malaria endemicity in the region. Active surveillance yielded a Plasmodium spp. slide-positive prevalence of 4.2% (43 of 1,023) and a polymerase chain reaction (PCR)–positive prevalence of 17.6% (144 of 819). Plasmodium vivax prevalence was 2.9% and 14.2% while Plasmodium falciparum prevalence was 1.3% and 2.6% by microscopy and PCR, respectively. Approximately two-thirds of slide-positive and one-fourth of PCR-positive people were symptomatic. Anemia was associated with slide positivity (P < 0.001) and PCR positivity for P. falciparum (P = 0.003). Sensitivity of field microscopy and agreement between field and reference laboratory microscopists were low, arguing for using PCR for epidemiologic investigation and malaria control. While these data confirm recent findings from the Brazilian Amazon suggesting that sufficient numbers of asymptomatic malaria parasitemic patients are present to form a persistent reservoir for continuous reinfection within the Peruvian Amazon region, these results also indicate that clinical immunity in human populations can be driven in malaria-endemic regions that do not have high intensity malaria transmission

Acute undifferentiated febrile illnesses are common in tropical developing countries but are difficult to diagnose on clinical grounds alone. Leptospirosis is rarely diagnosed, despite evidence that sporadic cases and epidemics continue to occur worldwide. The purpose of this study was to diagnose an outbreak of acute undifferentiated febrile illness among Peruvian military recruits that developed after a training exercise in the high jungle rainforest of Peru. Of 193 military recruits, 78 developed an acute febrile illness with varied manifestations. Of these, 72 were found to have acute leptospirosis by a microscopic agglutination test (MAT). An enzyme-linked immunosorbent assay using Leptospira biflexa antigen was insensitive for the detection of anti-leptospiral IgM antibodies compared with the MAT (20 of 72, 28%). This outbreak of acute undifferentiated febrile illness among Peruvian military recruits was due to leptospirosis. High clinical suspicion, initiation of preventative measures, and performance of appropriate diagnostic testing is warranted in similar settings to identify, treat, and prevent leptospirosis.

Eighty-nine Amblyomma variegatum ticks were collected from the islands of St. Kitts and Nevis in the Caribbean and preserved in 70% ethanol or local rum. After being washed in sterile water, their DNA was extracted and analyzed by a polymerase chain reaction (PCR) for DNA of spotted fever group rickettsiae and ehrlichiae. None of the tested ticks was positive in a PCR assay using the primers 16S EHRD and 16S EHRR for the 16S rRNA gene of Ehrlichia spp.. Forty-one percent of the A. variegatum (36 of /89 of which 34 [47%] of 72 were adult males, 2 (13%) of 16 were adult females, and 0 (0%) of 1 were nymphs) were positive in a PCR assay using the primer pair 190-70 and 190-701 for the outer membrane protein A (ompA) gene of spotted fever group rickettsiae. All PCR amplification products obtained had 100% sequence homology with Rickettsia africae, the agent of African tick-bite fever.

Two scrub typhus outbreaks occurred among U.S. Marines training at Camp Fuji, Japan, between October 25 and November 3, 2000 and October 17 and November 30, 2001. Nine cases in approximately 800 Marines in 2000 and eight cases in approximately 900 Marines in 2001 (approximate attack rates = 1.1% and 0.9%, respectively) reported with signs and symptoms of fever, rash, headache, lymphadenopathy, myalgia, and eschar. Serologies and rapid response to doxycycline treatment indicated they had scrub typhus. Sixty-four convalescent serum samples (18 suspected cases and 46 negative controls) from U.S. Marines training at Camp Fuji during the outbreaks were assessed by enzyme-linked immunosorbent assay (ELISA), rapid flow assay (RFA), and Western blot assay for evidence of infection with Orientia tsutsugamushi, the causative agent of scrub typhus. All but one suspected case had serologic evidence of scrub typhus and all 46 control sera were non-reactive to O. tsutsugamushi antigens. The recombinant 56-kD antigen (r56) from the Karp, Kato and Gilliam strains of O. tsutsugamushi in an ELISA format provided better results than Karp r56 alone (ELISA and RFA) or whole cell antigen preparation from Karp, Kato and Gilliam (ELISA).

Thirty-eight (designated as cases) of 60 Korean emigrants who consumed raw fresh water fish in Yangon, Myanmar developed migratory swellings and creeping eruptions on the back, abdomen, flank, and other cutaneous areas 1–10 weeks later. The symptoms included itching, nodule formation, fatigue, urticaria, fever, pain on the skin, and erythematous plaques. Skin biopsies of two cases revealed no parasites. However, the mean ± SD peripheral blood eosinophilia among the cases was 6.3 ± 6.5% (n = 29) and 9.0 ± 9.8% (n = 26) in two examinations. An enzyme-linked immunosorbent assay of their serum samples, using Gnathostoma doloresi adult worms as the antigen, showed mean ± SD optical densities of 0.47 ± 0.29 (n = 28) and 0.32 ± 0.20 (n = 30) in two examinations and 0.12 ± 0.09 (n = 50) in healthy controls. Two advanced third-stage larvae of G. spinigerum were found in two of six catfish purchased at a local market in Yangon. The outbreak of the human infection is suggested to have been due to G. spinigerum, which is known to live out its life cycle in the Yangon area of Myanmar.

Investigations on intestinal schistosomiasis were carried out in Yoro, a small village located in the transitional zone between forest and savannah, in the Mbam and Inoubou Division of Cameroon. Four human-water contact points were identified in the village and sampled for snails, and the inhabitants underwent parasitologic and clinical surveys to search for signs and symptoms of intestinal schistosomiasis. The results indicated the presence of two freshwater snails, both potential intermediate hosts of Schistosoma sp: Biomphalaria pfeifferi and Bulinus forskalii. However, only the former species was incriminated in the transmission of the disease, with the prevalence of snail infection being 10% (1 of 10) and 14.3% (2 of 14), respectively, during surveys 1 (in the dry season) and 2 (in the rainy season). The overall prevalence of Schistosoma mansoni eggs in stool samples was 54.4% (98 of 180). The mean ± SD intensity of infection was 100.3 ± 114.7 eggs per gram of stool. Eggs of S. intercalatum were not detected during parasitologic examination of stool specimens. In Cameroon, it appears that unlike the distribution of S. mansoni, which usually follows that of B. pfeifferi, B. forskalii is commonly found where S. intercalatum does not exist due to competitive exclusion through introgressive hybridization. Of the 180 people included in the study, 52.3% reported abdominal pain and 37.5% had bloody stools. Splenomegaly and hepatomegaly were noted in 11.7% and 3.9%, respectively, of the subjects examined. Three foci of S. mansoni were previously described in the Mbam and Inoubou Division, including Bafia town, Makenene, and Kinding Djabi villages. With the present focus in Yoro, the Mbam and Inoubou Division appears to be the most important endemic zone of S. mansoni in southern Cameroon.

We evaluated a recombinant virus chimera, ChimeriVax-WN, in which the West Nile virus (WNV) surface protein genes (pre-membrane [prM] and envelope [E]) are substituted into the genome of the 17D vaccine strain yellow fever virus (YF-17D), as a vaccine candidate for protection of birds from WNV disease. Using fish crows (Corvus ossifragus) as a model, we found that none of eight crows that received two high doses of vaccine (approximately 100,000 plaque-forming units [PFU]) developed viremia and only one developed WNV-neutralizing antibodies. When challenged with subcutaneous injection of 2,000 PFU of WNV (NY99 strain), all eight developed viremia levels similar to unvaccinated control birds (n = 4). Two of the vaccinated birds died of the infection, compared with no mortality in the four controls. To further investigate the failure of the vaccine, we inoculated chickens with both the vaccine and YF-17D and found no evidence of replication with either of these viruses. These data indicate that this vaccine candidate failed to protect birds from the morbidity and mortality attributed to WNV infections. However, if used in mammals, this recombinant viral vaccine is unlikely to inadvertently enter a natural transmission cycle with birds as amplifying hosts.

An epidemic-geographic rabies study was carried out in which 72 animal and human brain samples were analyzed for Lyssaviruses by a direct immunofluorescent technique (DIFT) and a reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Fifty-two samples were also tested by a mouse inoculation test. Lyssavirus RNA was detected in 60 of 72 samples. Five DIFT-negative bat samples tested by a nested PCR assay showed evidence of the presence of rabies virus RNA. Sequencing of amplified rabies virus nucleoprotein encoding segments of a selection of the samples resulted in the formation of clusters, corresponding to samples originating from cattle and equines from the same hydrographic basin. Genomically related Lyssavirus strains of bat origin were found in each cluster, most likely because of the role of the bat in the epidemiology of the virus. All samples studied were of genotype 1. With exception of the human sample, all were distinct from the reference sample.

While basophilia is often found in animal models of parasitic infection, it has not yet been established whether it occurs in parasite-infected humans. We investigated the relationship between basophilia and parasitic infections in humans by reviewing charts from 668 patients with confirmed parasitic infection (472 with only helminths, 146 with only protozoa, and 50 with both helminth and protozoan infections) and from 50 patients without parasitic infections. Basophilia (> 290 cells/mm3 ) occurred in only four of the 668 parasite-infected patients (0.6%), and there were no statistically significant differences in the percentages of patients with basophilia or in the absolute basophil counts among either the helminth-infected, protozoa-infected, or uninfected populations. Analysis with regard to relative basophil levels revealed that basophils constituted more than 3% of the peripheral white blood cell population in only four patients. Thus, basophilia occurs only rarely in human parasitic infections and is consequently not a useful clinical marker in the evaluation of suspected parasitic disease.

We evaluated the completeness and differential ascertainment of vital events in children less than five years old registered in two rounds of a demographic surveillance system (DSS) in western Kenya using a two-sample capture-recapture. The primary lists consisted of births and child deaths identified by two rounds of the DSS conducted in October 2000 and August 2001. The secondary lists consisted of births and child deaths identified independently from two surveys of 5,000 randomly selected households conducted immediately after each DSS round, covering the same population over the same time period. Analysis of the overlap between lists yielded the following sensitivities for the two DSS rounds: 62% and 49%, respectively, for identifying neonatal deaths (<1 month); 72% and 78%, respectively, for post-neonatal child deaths (1–59 months); and 88% and 78%, respectively, for identifying newborns. Female deaths were less likely to be reported than male deaths. The primary limitation of using capture-recapture in this setting was difficulty in matching between lists due to inconsistent dates of birth and death and variability in spelling of names. Assuming limitations of current methods are sufficiently addressed, capture-recapture appears to be a useful tool in evaluating DSS completeness and differential ascertainment of vital events.