The American Journal of Tropical Medicine and Hygiene - Volume 60, Issue 4, April 1999

We carried out a seroepidemiologic survey to define the prevalence of human T cell lymphotropic virus types 1/2 (HTLV-1/2) infections among aboriginal populations from isolated regions of northern Argentina and the Amazon region of Peru. Antibodies against HTLV were measured with agglutination tests and confirmed with by an immunofluorescence assay (IFA) and Western blotting. Five (6.94%) of 72 samples from the Tobas Indians in Argentina were positive by the IFA; two samples were typed as HTLV-1 (2.78%), two as HTLV-2 (2.78%), and one (1.39%) could not be typed because it had similar antibody titers against both viruses. No positive samples were found among 84 Andinos Puneños and 47 Matacos Wichis Indians. Seroprevalences of 2.50% (1 of 40) and 1.43% (1 of 70) for HTLV-1 were observed among Wayku and San Francisco communities in the Amazon region of Peru, and seroprevalences of 4.54% (1 of 22) and 2.38% (1 of 42) for HTLV-2 were observed among Boca Colorada and Galilea communities. No serologic evidence of human immunodeficiency virus (HIV) infection was found among the Indians tested. These results indicated the presence of HTLV-1 and HTLV-2 in the indigenous populations of Argentina and Peru. Moreover, the lack of HIV infection indicates that the virus has probably not yet been introduced into these populations.

Phylogenetic analysis of 20 strains of Venezuelan equine encephalitis (VEE) virus subtype IE isolated from 1961 to 1996 in Mexico and throughout Central America showed that VEE virus subtype IE was monophyletic with respect to other VEE virus subtypes. Nonetheless, there were at least three distinct geographically separated VEE virus IE genotypes: northwestern Panama, Pacific coast (Mexico/Guatemala), and Gulf/Caribbean coast (Mexico/Belize). Strains from the Caribbean coast of Guatemala, Honduras, and Nicaragua may cluster with the Gulf/Caribbean genotype, but additional isolates from the region between Guatemala and Panama will be required to firmly establish their phylogenetic position. Viruses associated with two separate equine epizootics in Mexico in the 1990s were phylogenetically related to nonepizootic viruses from neighboring Guatemala and may represent the emergence or re-emergence of equine-virulent VEE virus subtype IE in Middle America.

A large-scale longitudinal cohort project was initiated in western Kenya in June 1992. The primary purpose of the project was to study Plasmodium falciparum malaria in a highly endemic area using a comprehensive and multidisciplinary approach, which included epidemiology, entomology, and immunology. Between June 1992 and July 1994, pregnant women living in 15 rural villages were identified during a monthly census and 1,164 were enrolled. The women were followed-up throughout their pregnancy and they, along with their newborn infants and direct siblings of the infants' less than 15 years of age, were monitored over time. As of May 1995, 1,017 infants had been born to these women. This paper presents the design and general methodology used in this study and describes the initial experience with intense monitoring of a large population over a prolonged period.

A large-scale longitudinal cohort project was initiated in western Kenya in June 1992. Between June 1992 and July 1994, 1,848 children less than 15 years of age were monitored prospectively for a mean of 236 days. During this period, 12,035 blood smears were examined for malaria and only 34% were found to be negative. Parasite prevalence (all species) decreased with age (from a high of 83% among children 1-4 years old to 60% among children 10-14 years old). Even more dramatic decreases were noted in the prevalence of high density falciparum infection (from 37% among children 12-23 months old to < 1% among 10-14-year-old children) and in clinical malaria (20% to 0.3% in the same age groups). Children < 1 year of age accounted for 55% of all cases of anemia detected. Anemia was consistently associated with high density infection in children < 10 years of age (20% to 210% increased risk relative to aparasitemic children). These results demonstrate the relationship between high-density malaria infection and two clinical manifestations of malarial illness.

Anopheles pseudopunctipennis was collected from Acapulco, Mexico and Sallee River, Grenada, West Indies and used in cross-mating experiments. Larvae from the cross, Mexico female X Grenada male, died in the third instar. However, adult progeny were obtained from the reciprocal cross Grenada female x Mexico male. These hybrid males had testes with apparently normal appearance but some without viable sperm. Polytene chromosomes obtained from hybrid females exhibited extensive asynapsis of the X chromosomes. Previously undescribed fixed inversion differences between the two populations were noted on the X chromosome. It is concluded that the two populations belong to different species. The Grenada population is designated An. pseudopunctipennis species C, since it is the third taxon recognized in this species complex.

A clinical trial (n = 120, 60 males and 60 females) was conducted to assess the efficacy of an extended duration tropical insect/arthropod repellent (EDTIAR) topical formulation of N,N-diethyl-m-toluamide (DEET). The amount of EDTIAR (mean +/- confidence interval), applied by participants in accordance with label directions, was not significantly different between females (3.66 +/- 0.32 mg/cm2) and males (3.45 +/- 0.33 mg/cm2). There also was no significant difference in the number of Anopheles stephensi mosquitoes biting the control arm of females or males at 0, 3, 6, 9, and 12 hr. While gender had no effect on feeding, the time of day did effect mosquito feeding with fewer mosquitoes feeding in the afternoon than in the morning or evening. The percent protective efficacy at 0, 3, 6, 9, and 12 hr was 100.0, 99.3, 92.8, 79.7 and 66.3 for females, and 100.0, 100.0, 97.6, 91.9, and 77.5 for males. These data are inconsistent with the EDTIAR label claim that the repellent provides 95% or greater protection against mosquitoes for 12 hr or more under normal use conditions. The results of a multivariate regression analysis indicated that 1) protection decreased linearly as time after application of repellent increased (P < 0.001), 2) individuals who applied higher doses of repellent were better protected against mosquito bites (P < 0.001), 3) females experienced significantly less protection over time than did males (P = 0.005), and 4) the estradiol concentration in the blood had no effect on efficacy of the repellent (P = 0.110).

We measured the concentrations of several serum and urinary fibrosis markers, which are metabolites of extracellular matrix, in schistosomiasis patients to investigate their relationship with the ultrasonographic scoring system and with parasitologic data. This study was conducted in patients with various stages of the disease evaluated by ultrasonography (intestinal disease with no organ involvement, with minor hepatosplenic involvement and with severe disease) and in endemic controls. The level of hyaluronan, which were increased in infected patients compared with controls (P < 0.01), was the only fibrosis marker that correlated with the ultrasonographic score (P = 0.003) and is thus a potential serum marker of schistosomiasis-associated morbidity. Urinary free pyridinoline levels were lower (P < 0.001) in infected patients with fibrosis (score > or = 1) than in nonfibrotic patients. A two-year follow-up of the patients treated with praziquantel showed that type I collagen and hyaluronan decreased during the first year post-treatment, whereas free pyridinolines peaked after 12 months and decreased thereafter.

A 37-year-old woman with a known history of longstanding neurocysticercosis presented with a three-day history of new onset headache. Several years prior to her current presentation, she had undergone cysticidal treatment and was assumed to be cured of active disease. Computed tomography and magnetic resonance imaging studies done three months prior to presentation showed multiple intracerebral calcified lesions consistent with resolved neurocysticercosis. Physical and laboratory findings were noncontributory. Imaging studies showed the same previously calcified lesions, but they were now surrounded by large amounts of edema. This case represents a unique report of reactivation of neurocysticercosis and raises interesting questions about the natural history of this infection.

Because microvascular damage is a common feature of cerebral malaria, we have examined the role eicosanoid metabolites (prostaglandins and leukotrienes) in experimental cerebral malaria. Eighty ICR mice were infected with Plasmodium berghei ANKA, with 40 uninfected mice as controls. Half of the infected mice were treated on days 4 and 5 with aspirin, a prostaglandin synthesis inhibitor. Infected mice started to die of cerebral malaria on day 6, and by day 17, all infected mice died. In contrast, all infected mice treated with aspirin died by day 12. Infected mice had increased phospholipase A2 mRNA expression in the spleen and cyclooxygenase 1 (COX1) and COX2 expression in the brain. At the peak of cerebral malaria, infected mice had higher serum leukotriene B4 levels than control mice, and aspirin-treated infected mice had higher serum leukotriene B4 levels than untreated infected mice. These results suggest that prostaglandins are protective whereas leukotrienes are detrimental in cerebral malaria.

In Brazil, two types of activities have led to the worsening of malarial transmission in the Amazon region: prospecting/mining and agricultural settlements. In the present study, we analyze the cellular response of 52 of these individuals (14 gold-miners and 38 farmers) living within the same endemic area. Two Plasmodium falciparum major surface antigens (recombinant proteins) were used for cellular proliferative assays: circumsporozoite protein and merozoite surface protein-1. The frequency of these cellular responses were significantly higher among the miners (57-64%) than the farmers (10-20%) when either recombinant protein was used. Our data suggest that a higher exposure to malaria of the gold-miners contributed to their higher in vitro cellular response compared with the farmers. These findings point the way to further studies evaluating the influence of risk factors associated with the life styles of different social groups and the immune responses to these antigens.

The frequency of cytokine-producing peripheral blood mononuclear cells was assessed in 28 subjects with microfilaremic loiasis and in 14 amicrofilaremic individuals. In addition, a subgroup of seven microfilaremic individuals coinfected with Plasmodium malariae was evaluated. By using flow cytometry for the intracellular detection of cytokines, a more pronounced T helper (Th)2 cell-type response with the expansion of interleukin (IL)-4, IL-10, and IL-13 expressing CD4+ cells in the microfilaremic compared with the amicrofilaremic group was noted. Expression of IL-5 was equivalent in both groups as was the frequency of Th2-type cytokines expressing CD8+ cells and of Th1-type cytokines (interferon [IFN]-gamma, IL-2, IFN-gamma/IL-2) producing CD4+ and CD8+ cells. Th0-type cytokine-expressing cells, represented by IL-4/IFN-gamma, IL-10/IFN-gamma, and IL-13/IFN-gamma, were equally distributed within groups. Coinfection of P. malariae did not significantly alter the cytokine expression compared with microfilaremic individuals without P. malariae infections. By identifying a large panel of cytokine-producing T cell subpopulations, a Th2-driven immune response in microfilaremic Loa loa patients was noted.

A nested polymerase chain reaction (PCR) assay that uses Plasmodium genus-specific primers for the initial PCR (nest 1) amplification and either genus- or species-specific primers for the nest 2 amplifications was tested on laboratory and field samples. With in vitro cultured Plasmodium falciparum-infected blood samples, it was capable of detecting six parasites/microl of blood using DNA prepared from 25-microl blood spots on filter paper. The assay was evaluated on fingerprick blood samples collected on filter paper from 129 individuals living in a malaria-endemic area in Malaysia. Malaria prevalence by genus-specific nested PCR was 35.6% (46 of 129) compared with 28.7% (37 of 129) by microscopy. The nested PCR detected seven more malaria samples than microscopy in the first round of microscopic examination, malaria in three microscopically negative samples, six double infections identified as single infections by microscopy and one triple infection identified as a double infection by microscopy. The nested PCR assay described is a sensitive technique for collecting accurate malaria epidemiologic data. When coupled with simple blood spot sampling, it is particularly useful for screening communities in remote regions of the world.

A commercial capture ELISA for specific IgM and IgG antibodies produced during dengue infection (PanBio Dengue Duo) showed excellent sensitivity (99%, n = 78) using sera collected at hospital discharge compared with established ELISA and hemagglutination inhibition (HAI) assays. Furthermore, the ELISA was able to diagnose 79% of the dengue cases using sera collected at hospital admission. The ELISA also showed high specificity (92%) in paired sera from patients without flavivirus infection (n = 26), although 45% of the patients with Japanese encephalitis (n = 20) showed elevation of IgG but not IgM. The IgG capture ELISA showed good correlation with the HAI assay (r = 0.83, P < 0.0001), and IgG levels could be used to distinguish between primary and secondary infection, with 100% of primary infections and 96% of secondary infections being correctly classified. This ELISA should prove useful in the clinical diagnosis of dengue infections.

Borrelia burgdorferi is transmitted in an enzootic cycle in Colorado between the tick Ixodes spinipalpis and the woodrat Neotoma mexicana. The genetic relationship of Colorado isolates to other B. burgdorferi isolates is unknown nor have relationships among various Colorado isolates been determined. Portions of the flagellin (fla), 66-kD protein, and outer surface protein A (ospA) genes were amplified from 71 Colorado isolates, screened for genetic variability using single strand conformation polymorphism analysis, and unique alleles were sequenced. Colorado isolates were most similar to tick isolates from California and New York isolate 25015. Genetic distances among Colorado ospA sequences were the same or higher than distances among other isolates whereas distances among fla sequences tended to be the same or lower. The index of association (I(A)) was calculated among all loci as a measure of clonality. The I(A) among Colorado isolates was similar to I(A) previously estimated among other United States isolates.

The mechanism for long-term maintenance of western equine encephalomyelitis (WEE) virus in California was investigated by studying genetic variation in the E2 portion of the genome of 55 strains of WEE virus isolated since 1938 from different locations in California. Four major lineages were evident: virus strains isolated from the Central Valley since 1993 and Los Angeles in 1991 formed lineage A; southern California strains isolated since 1978 and isolates from the Central Valley from 1978 to 1987 formed lineage B; northern California isolates from 1968 to 1971 formed lineage C; and early isolates from 1938 to 1961 formed a fourth lineage, D. The separation of strains from north and south of the Tehachapi and San Bernardino Mountains (i.e., the Central Valley and southern California, respectively) since 1991 indicates that there has been little recent movement of virus between the two regions and recent strains from these two locations appear to be evolving independently. However, within the Central Valley and within southern California, virus appears to circulate freely, perhaps by movement of birds or mosquito vectors. Although the current virus lineage in the Central Valley may have been introduced from an unknown source in 1991, introduction and establishment of new viral genotypes from outside California do not seem to occur regularly. It appears most likely that virus is maintained in separate geographic areas of California through local persistence in enzootic foci.

The aim of this study was to analyze the association of hepatocellular carcinoma (HCC) with hepatitis C virus (HCV) in Egypt, using hepatitis B virus (HBV) and hepatitis E virus (HEV) as virus controls. In addition, the association of HCC with HCV RNA levels among persons seropositive for HCV was analyzed. We compared 131 patients with proven HCC, 247 with bladder cancer, and 466 healthy hospital employees. Age, sex, and place of residence were recorded to study confounding factors. Among the healthy controls, 16% were seropositive for HCV, 21% for HBV, and 31% for HEV. When healthy controls were age-matched with HCC patients, the latter were significantly (P < 0.001) more often HCV seropositive (67%) than were the controls (30%). The seropositivity for HBV and HEV did not differ significantly in frequency between the two groups. The seropositivity for HCV was also significantly (P < 0.001) more often found in HCC patients (76%) than in BC patients (47%), with seroprevalences for HBV and HEV not differing significantly in these age-matched groups. In HBV-negative HCC and bladder cancer patients, seroprevalence for HCV was significantly (P = 0.002) higher in HCC patients (68%) than in bladder cancer patients (36%). This difference was even more pronounced (P < 0.001) in HBV-positive HCC and bladder cancer patients (78% versus 52%, respectively). Of HCV-seropositive individuals, 49% were HCV RNA positive by branched DNA assay, and of these, 96% were infected by HCV genotype 4. No correlation between HCV RNA load and seropositivity of HBV or age or disease state was found. Infection with HCV and HCV-HBV double infection, but not HBV or HEV infection alone, is strongly correlated with HCC in Egypt.