The American Journal of Tropical Medicine and Hygiene - Volume 54, Issue 1, 1996

The year 1995 was the busiest and perhaps the most complex in the history of the American Journal of Tropical Medicine and Hygiene. A record total of 390 manuscripts was submitted to the Journal for review and possible publication. More than 60% of these reports were submitted by colleagues from outside the United States. We welcome the participation of our overseas colleagues and are pleased with the strength we derive from their contributions to the Journal.

In response to substantial increases in printing and mailing costs, we made the difficult decision to increase subscriber rates for the Journal after many years without such a change. This move should increase the stability of our financial position. While the new rates are competitive with other publications in the field, any increase presents problems for libraries, and we will need the input from Society members in encouraging their institutional associations to continue to subscribe to the Journal. Subscriber income is a major part of our financial base.

Material for publication should be sent to the Editor, McWilson Warren, 3088 Briarcliff Road, Suite A11, Atlanta, Georgia 30329, USA. Such material should be accompanied by a letter from the corresponding author with signatures from all submitting authors indicating that they have participated in and concur with the submission and that the material has not been, and will not be, submitted elsewhere for publication as long as it is under consideration of the JOURNAL. Manuscripts and letters to the Editor should be typewritten, letter quality, in 10 point type, on one side of the paper and submitted in quadruplicate. Paper should be 8 1/2 × 11 inches, pages should be numbered, and the manuscript should be neither stapled nor folded. Double spacing should be used throughout including in the list of references, tables and figure legends. Tabular or other material that has been reduced by xeroxing is not acceptable.

Hypokalemia in leptospirosis acute renal failure (ARF) was studied in nine patients with severe leptospirosis ARF and five patients with moderate leptospirosis ARF and compared with five patients with severe acute tubular necrosis (ATN) and eight healthy individuals. Urinary volumes of both the severe and moderate leptospirosis groups were higher than those of the severe ATN group. Leptospirosis groups had serum potassium levels lower than those found in the healthy and severe ATN groups. Serum sodium levels were lower in the severe leptospirosis group than in the moderate leptospirosis, the severe ATN, and the healthy groups. There was a positive correlation between the fractional excretion of sodium and potassium in the severe leptospirosis group as well as between serum creatinine and potassium levels in the pooled leptospirosis groups. Urinary pH in the severe and moderate leptospirosis groups was lower than in the severe ATN group. Aldosterone levels were higher in the severe leptospirosis group than in the healthy individuals. Cortisol levels were higher in the leptospirosis groups than in the healthy subjects. These results strongly suggest that hypokalemia in leptospirosis ARF is due to renal potassium wasting potentialized by aldosterone and cortisol, requiring that special attention is given to potassium replacement as well as to volume repletion in the treatment of leptospirosis ARF.

To characterize the immune dysfunction associated with paracoccidioidomycosis, we studied the in vitro lymphocyte reactivity to phytohemagglutinin (PHA), pokeweed mitogen (PWM), a Candida albicans antigen (CMA), and a Paracoccidioides brasiliensis antigen (PbAg) in 32 patients with the acute and the chronic form of the disease before or during the initial phase of treatment and after clinical cure. We also studied, as controls, 30 healthy individuals, 15 of them immune to P. brasiliensis. Results showed a strong hyporesponsiveness to the PbAg while responses to mitogens and CMA were comparable with those of controls. Patients with the acute form of the disease (usually more severe) had more marked PbAg hyporesponsiveness than those with the chronic form. After patients' clinical cure, PbAg proliferative responses were similar to controls and greater than those seen before pretreatment. Changes in other parameters were also seen in the treated patients: skin test anergy to paracoccidioidin, high levels of anti-P. brasiliensis antibodies, leukocytosis, and eosinophilia. These changes were usually more intense in patients with the acute form of the disease. The post-treatment CD4+, CD8+, and total lymphocyte counts were similar to those of controls. Correlation between these parameters and the lymphoproliferative responses to the various stimuli was only found with PbAg: PbAg responses correlated inversely with eosinophil and anti-P. brasiliensis antibody levels. Overall, our results demonstrate an antigen-specific cellular immunity defect, which is reversible with treatment and possibly related to a T helper cell-2 pattern of immune response during active disease.

The role of antibodies in the previously demonstrated harmful effect of Trypanosoma cruzi-infected mothers on progeny infection was studied by injecting either serum from chronically infected animals or purified T. cruzi-specific antibodies into uninfected mice during gestation and lactation periods. It was verified that injected antibodies were transferred to offspring. Pregnant or lactating animals exhibited lower circulating antibody levels than nonpregnant or pregnant but nonlactating mice, respectively, suggesting that such antibody transfer occurred in both fetuses and suckling offspring. When infected two months after birth, offspring of mice treated with chronic serum or purified antibodies displayed significantly higher parasitemia than offspring from mothers receiving control serum or immunoglobulins unrelated to T. cruzi. These results indicate that soluble factors contained in sera of infected mice, and particularly antibodies, when transferred from mothers to their young, are able to worsen T. cruzi acquired infection in the offspring.

A polymerase chain reaction (PCR) typing technique, based on the amplification of polymorphic regions from the merozoite surface protein 1 (MSP-1) and MSP-2 Plasmodium falciparum genes, was used to characterize parasites collected in a longitudinal study of asymptomatic carriers of malaria parasites living in two distinct epidemiologic situations. Blood samples were collected from children and adults living in the village of Dielmo, Senegal, when malaria transmission was 3–6 infective bites/week/individual. For each individual, every sample collected at two-week intervals over a period of three months showed a specific PCR pattern. Changes involved both appearance and disappearance of specific alleles. Analysis of blood samples collected at a few-days interval showed that modifications of the PCR patterns occurred rapidly. Most alleles were detected over a period of 2–3 weeks, but some alleles could be detected only for a few days. The frequent modifications of the PCR patterns indicate significant changes in allelic balance over time, and importantly, this was observed both in children and adults. These results strongly contrast with the stability of the parasite types harbored by asymptomatic individuals living in Pikine, Senegal during a period in which malaria transmission was interrupted, and therefore suggest that the rapid turnover observed in Dielmo may reflect the introduction of new parasite populations by mosquitoes.

Several methods have been suggested to identify schistosome cercariae. In the present work, a new method is proposed, based on the analysis of the distribution of sensory endings (sensillae) on the body of the cercariae, revealed by an impregnation with silver nitrate. We determined the mutual distances between the sensillae and calculated the mean values, standard deviations, coefficients of asymmetry, and of kurtosis of the distribution of these mutual distances. Applied to two species, Schistosoma mansoni from Brazil and S. intercalatum from Cameroon, these mutual distances had the same mean value and the same standard deviation but quite different coefficients of symmetry (0.34 ± 0.11 versus 0.73 ± 0.08; P < 0.0001) and of kurtosis (-0.82 ± 0.27 versus -0.58 ± 0.31; P < 0.0001). The latter two indices were therefore very effective for discriminating the two species. The present method can be applied to other species and to hybrids in the field.

Onchocerca volvulus and O. lienalis skin-derived microfilariae (mf) were cultured in vitro; parasite viability was assessed at intervals by measuring their ability to develop in Simulium ornatum. In the presence of monkey kidney feeder cells, both species retained full viability when cultured for up to 5 hr before intrathoracic injection into Simulium. In the absence of feeder cells and in contrast to O. lienalis, O. volvulus mf rapidly lost their viability. In further trials (including feeder cells), O. volvulus mf retained full viability for 14 days, while O. lienalis mf retained full viability for at least 19 days but with a proportion able to develop to third-stage larvae (L3) after 70 days in culture. In experiments using this system to culture O. volvulus mf (ex utero) derived from adult female worms but with the addition of reduced glutathione and/or 20-hydroxyecdysone, parasites were consistently more active over a 70-day period than those cultured without these additives. None of the mf cultured without additives were able to develop to L3 in Simulium when tested for up to 51 days in culture, while a proportion of mf incubated with reduced glutathione and/or 20-hydroxyecdysone produced small but significant numbers of L3 after 28, 43, and 51 days, representing the first time that uterine mf have been cultured to a form infective for the vector.

With the recent resurgence in the interest and use of maggot therapy, blow fly rearing can be expected to increase. The rearing of these necrophagous flies is technically simple, but can be expensive, malodorous, and wasteful of space. Although there are numerous references to maggot rearing in the older literature, they do not adequately address these specific problems. Therefore, we describe several of the simple, low-cost, and unobtrusive strategies for rearing blow flies that have proven useful in our hospital-based insectary.

Lutzomyia trapidoi is the major vector of cutaneous leishmaniasis in Ecuador. In the framework of an epidemiologic study, female Lu. trapidoi sand flies were captured on human bait in La Tablada and Paraiso Escondido. Some coloration heterogeneity among the specimens caught led us to look for the existence of cryptic species using multilocus enzyme electrophoresis. In 196 specimens studied, five of seven enzyme loci proved to be variable, making it possible to check for departures from panmixia both by Hardy-Weinberg statistics and linkage disequilibrium analysis. Two discrete groups were clearly distinguished, which could be differentiated by the diagnostic locus glycerophosphate dehydrogenase. The two groups occurred in sympatry within each locality. Genetic distances measured between these two groups were consistent with values usually found between distinct species. These results suggest the existence of at least two sibling species in Paraiso Escondido as well as La Tablada. The epidemiologic relevance of these results is discussed.

Morphologically identified Anopheles flavirostris (Diptera: Culicidae), the principal malaria vector in the Philippines, comprised two species in collections from the Bataan Province of Luzon based on allozyme and internal transcribed spacer 2 ribosomal DNA analysis. Seven percent of morphologically identified specimens were the closely related nonvector An. filipinae. Morphologic variability of An. filipinae may account for some of these misidentifications. Genetic identification tools promise to be useful not only for verifying the identification of morphologically defined taxa but also for detecting the presence of morphologically indistinguishable sibling species in the Philippines.

Beginning in August 1990, approximately 800,000 coalition troops were deployed to the Persian Gulf during Operations Desert Shield and Desert Storm. There was substantial concern about arthropod-borne diseases, particularly sand fly fever and cutaneous leishmaniasis, because of high morbidity rates in the Persian Gulf during World War II (WWII). In sharp contrast to WWII, there was no report of sand fly fever among coalition forces and only 31 cases of leishmaniasis among 697,000 U.S. troops. To further evaluate the risk of arthropod-borne diseases, an entomologic survey was conducted in 12 areas of Kuwait and Saudi Arabia. A total of 1,556 arthropods was collected during four survey periods in 1992. The suspected vectors of cutaneous Leishmania major infection, sand fly fever, West Nile fever, Rift Valley fever, and Crimean-Congo hemorrhagic fever were identified; however, there was no evidence of arboviruses or Leishmania among collected specimens nor from 51 trapped rodents. There are several possible reasons for the low risk of arthropod-borne infectious diseases among Desert Shield/Storm troops in an area where suspected vectors frequently were found: the use of insecticides and repellents, and the deployment of most ground troops to the open desert during the cooler, winter period-conditions least favorable for the transmission of arthropod-borne diseases.

In the winter of 1992, some 402 Southeast Asian refugees were resettled in North Carolina. They received very limited medical screening before immigration and many arrived in the United States with significant health problems, including several tropical infectious diseases. These refugees had lived for many years in remote areas along the Vietnam-Cambodia border, where there is intense transmission of malaria, including Plasmodium falciparum resistant to most antimalarial drugs available in the United States. Of 322 refugees screened after arrival in North Carolina, 187 (58%) were infected: 33% with P. falciparum, 23.5% with P. vivax, 23.5% with P. malariae, and 2.1% with P. ovale. Most infected persons were asymptomatic and infections with multiple species were common. Because of the documented high infection prevalence and the probable presence of many subpatent infections, all nonpregnant refugees were treated with halofantrine; those with P. vivax or P. ovale infections were given primaquine as well. This group accounted for the largest cluster of malaria cases reported in the United States in the last 50 years. Their rapid relocation, with minimal medical screening prior to arrival, resulted in a significant burden to the refugees and to the health-care system. Coordination between immigration agencies, the public health community, and medical workers in communities where the refugees are settled is critical for U.S.-based management of imported tropical diseases.

Iodine deficiency is well known as a cause of several disorders such as endemic goiter and cretinism, along with a wide spectrum of psychoneurologic development disorders including endemic mental deficiency, which are generally correlated with damage to the fetus. Since as much as 40% of the Tanzanian population is at risk for iodine deficiency disorders (IDD) because they live in iodine-deficient areas, and although the effects of iodine deficiency on human reproduction in Tanzania have not been objectively studied, it is estimated that there are approximately 600,000 cretins and cretinoids in the country as a result of IDD. As a baseline study for future research on iodine deficiency and its effects on human reproduction in Tanzania, we assayed serum thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), and free thyroxine (FT4) in 93 clinically euthyroid pregnant women and 34 nonpregnant women as controls. Pregnancy was accompanied by significantly increased levels of total T3 and T4, decreased FT4, and increased TSH concentrations in serum. However, biochemical euthyroidism (assessed by FT4 and basal TSH) was demonstrated in almost all (99%) of the pregnant subjects in conformity with most of the previous findings elsewhere. We conclude that pregnant Tanzanian women residing in areas without iodine deficiency experience changes in biochemical parameters of thyroid function similar to their counterparts in other places.

The therapy of Plasmodium falciparum malaria continues to be a problem in many parts of Southeast Asia because of multidrug resistance to nearly all existing antimalarial drugs. Atovaquone is a novel hydroxynaphthoquinone with broad spectrum anti-protozoal activity. We recently evaluated the antimalarial activity of atovaquone in a series of dose-ranging studies in 317 patients with malaria at the Bangkok Hospital for Tropical Diseases. Originally, the drug was administered alone. Using atovaquone alone resulted in satisfactory, initial clinical responses in all patients; the mean parasite and fever clearance times were 62 and 53 hr, respectively. However, irrespective of the duration of therapy, overall cure rates were approximately 67%. In vitro sensitivity studies on parasites taken from patients prior to treatment and at the time of recrudescence showed a marked decrease in susceptibility to atovaquone in the recrudescent parasites. To improve cure rates, atovaquone was administered in combination with other drugs with antimalarial activity. Proguanil and tetracycline were chosen due to laboratory evidence of potentiation; doxycycline was selected because it has a longer half-life than tetracycline. Although pyrimethamine did not show laboratory evidence of potentiation with atovaquone, it was chosen as an alternative inhibitor of dihydrofolic acid reductase with a longer half-life than proguanil. The clinical studies with these drug combinations confirmed the laboratory results with marked improvement in cure rates for proguanil, tetracycline, and doxycycline; pyrimethamine showed only minimal improvement. Proguanil was subsequently selected as the preferred drug partner because of its long record of safety and the ability to use the drug in pregnant women and children. Of the 104 patients with falciparum malaria treated with atovaquone plus proguanil for 3–7 days, 101 were cured and had virtually no adverse side effects. The combination of atovaquone and proguanil also was effective in eliminating erythrocytic forms of P. vivax, but parasitemia recurred in most patients.

Among strategies for the development of new antimalarials, a study of plants traditionally used in Africa against malaria has been pursued. Extracts obtained from the plants Azadirachta indica, Cinnamonum camphora, Lippia multiflora, Vernonia colorata, Guiera senegalensis, Combretum micranthum, and Ximenia americana, commonly used in Cote d'Ivoire by native healers for the treatment of malaria, were tested on two strains of Plasmodium falciparum: FcB1-Colombia (chloroquine-resistant) and F32-Tanzania (chloroquine-sensitive). Extracts were obtained after infusion and decoction, both techniques being used by most native healers. The antimalarial activities of the extracts were tested first by parasite 3H-hypoxanthine incorporation and second by visual evaluation of the activities of plant extracts on thin blood smears, which also permitted the determination of parasitic stages and parasite alteration. Among the seven plants tested, some had an apparent inhibitory effect on P. falciparum growth in vitro, while others seemed to be less efficient.

Oligonucleotide primers were designed to amplify a 490-basepair DNA fragment in the 5′ end of the pWb 12 repeated DNA sequence in Wuchereria bancrofti for specific amplification of W. bancrofti DNA by the polymerase chain reaction (PCR). A single microfilaria in 100 µl of blood or added to 1 ml of blood, a single third-stage larva in a pool of 20 uninfected mosquitoes, or 0.4 pg of W. bancrofti genomic DNA added to 100 µl of human blood or serum can be detected by this PCR method. The parasite DNA in human blood and hydrocele samples and in mosquitoes was isolated free of any PCR inhibitors using simple purification techniques. Detection of PCR products was carried out by agarose gel electrophoresis, followed by staining with ethidium bromide and visualization under ultraviolet illumination. The results indicate that the PCR method is species-specific, rapid, and more sensitive than that of DNA probes and routine microscopy.

Although Mali is situated in the African zone endemic for mycetomas, no report has been published on the characteristics of the disease in this country. We report a series of 54 cases observed in Bamako. The causative agents were Madurella mycetomatis in 20 patients, Leptosphaeria sp. in one patient, Actinomadura madurae in 12 patients, A. pelletieri in 15 patients, and Streptomyces somaliensis in three patients. In this series, the observed geographic distribution of the causative agents was in agreement with data on the causative agents and their geographic distribution in neighboring countries, and with those suggesting a relationship between the type of infectious agent and the annual rainfall.

An acquired condition resulting in arrested growth was reported in the 1950s and 1960s from along the Nile near Jinja in eastern Uganda. This became known as Nakalanga dwarfism, and an association with onchocerciasis was postulated. After control of onchocerciasis through larvaciding in this area some 30 years ago, no new cases have been noted. We now report this condition from western Uganda where its appearance seems to be a relatively recently event. Thirty-one persons with short stature, 15 years of age and older, were identified through household surveys in an area of Kabarole district with a high prevalence of onchocerciasis. Cases identified were matched with controls selected for age and sex from the nearest household. Cases of Nakalanga syndrome weighed significantly less and were shorter than controls. The Z scores for weight-for-age, weight-for-height, height-for-age, and body mass index were significantly less among cases. Other clinical features observed among cases included absence of secondary sexual characteristics, skeletal deformities, dental caries, and mental retardation. All cases and 22 (79%) controls had microfilariae of Onchocerca volvulus in skin snips. All community members interviewed were aware of the Nakalanga syndrome, and 93% believed it to be acquired sometime after birth. The possible association with onchocerciasis is discussed.

Aspects of the reservoir competence of four rodents for the Lyme disease spirochete, Borrelia burgdorferi, were evaluated in California. Rodents were live-trapped and ear-punch biopsies were cultured during each season. A second set of biopsies was cultured from representative individuals after 2–3 weeks of captivity and the results of culturing biopsies taken on both dates were compared with the results of feeding Ixodes pacificus larvae on hosts xenodiagnostically. The prevalence of infections did not differ significantly between dusky-footed woodrats (Neotoma fuscipes) and California kangaroo rats (Dipodomys californicus) nor among seasons. Combined results of the three tests showed that 85.7% of dusky-footed woodrats (n = 21) and 78.6% of California kangaroo rats (n = 14) were infected with B. burgdorferi. In contrast, only 22.2% of brush mice (Peromyscus boylii) (n = 14) and 7.1% of pinyon mice (P. truei) (n = 9) were infected. The sensitivity of culturing ear-punch biopsies as an assay for borrelial infection was significantly greater when biopsies were taken after a short period of captivity (0.89) rather than on the day of capture (0.52). Tick xenodiagnosis, in which I. pacificus was used as the vector, revealed borrelial infections in 90.3% of infected rodents. Spirochetes were observed in 37.7% of 239, 45.2% of 155, 60.0% of 10, and 7.1% of 14 cultures of nymphal I. pacificus fed as larvae on naturally infected woodrats, kangaroo rats, brush mice, and a pinyon mouse, respectively. The mean prevalence of infection in xenodiagnostic ticks varied significantly among host species with a greater proportion of ticks infected while feeding on woodrats and kangaroo rats than on mice. This study reconfirms previous reports that implicated woodrats and kangaroo rats as reservoirs of B. burgdorferi in California.