The American Journal of Tropical Medicine and Hygiene - Volume 72, Issue 3, 2005

Polymerase chain reaction (PCR)–based methods were used to investigate malaria in pregnant women residing in Yaoundé, Cameroon. Microscopy and species-specific PCR-based diagnosis show that at delivery 82.4% of the women were infected with Plasmodium falciparum (27.5% blood-smear positive and 54.9% submicroscopic infections). The prevalence of P. malariae and P. ovale was 7.6% and 2.5%, respectively, with 9.4% infected with more than one species. Based on genotyping of the merozoite surface protein 1 (msp-1) and msp-2 alleles, the mean number of genetically different P. falciparum parasites in peripheral blood was 3.4 (range = 1–9) and 3.5 (range 1–8) in the placenta. Plasmodium falciparum detected by microscopy and PCR as well as mixed-species infections were significantly higher in women ≤ 20 years old and paucigravidae, but maternal anemia was associated only with microscopic detection of parasites. Neither submicroscopic infections nor number of parasite genotypes decreased significantly with age or gravidity. Thus, pregnancy-associated immunity helps reduce malaria to submicroscopic levels, but does not reduce the number of circulating parasite genotypes.

Between 1996 and 2001, the prevalence of placental malaria in pregnant women living in Yaounde, Cameroon and its effect on pregnancy outcome were evaluated with respect to gravidity and maternal age. Results showed that 19.9% of the women had placental malaria at delivery. After adjusting for relevant covariates, the major risk factor for placental malaria was an age < 25 years old. Placental malaria significantly increased the prevalence of anemia in women regardless of gravidity or age. In addition, the mean infant birth weight was lower and the percentage of pre-term deliveries (PTDs) and low birth weight (LBW) babies were higher in primigravidae and women < 20 years of age who had placental malaria. However, in a multivariate regression model taking relevant covariates into consideration, the major risk factor for PTDs was maternal anemia, and maternal anemia as well as first and second pregnancies were important risk factors for LBW babies.

We compared malaria indicators among sympatric groups to study human heterogeneities in the response to Plasmodium falciparum malaria infection. Four cross-sectional surveys and two longitudinal surveys in two sympatric ethnic groups (Dogon and Fulani) in Mali were carried out from 1998 to 2000. Spleen and parasite rates were evaluated during the cross-sectional surveys and disease incidence was assessed during longitudinal surveys. In spite of similar sociocultural factors and entomologic inoculation rates between ethnic groups, the Fulani had a significantly higher spleen enlargement rate, lower parasite rate, and were less affected by the disease than the Dogon group, whose frequency of hemoglobin C was higher than that recorded among the Fulani group. The Fulani group had significantly higher levels of IgG and IgE against crude malaria antigen than the Dogon group, suggesting a role of anti-malaria antibodies in the immune protection seen in this group.

The practical advantages of sampling and storing blood on filter paper for analyses of human and pathogen genes highlight the need for reliable, sensitive, and cost-effective DNA extraction methods. We describe a new Tris-EDTA (TE) buffer-based method for extraction of DNA from blood dried on filter paper. The method was evaluated against the commonly used methanol and Chelex® methods, regarding polymerase chain reaction detection of Plasmodium falciparum parasites from samples stored for 1–2 years. The sensitivity of detection was dependent on the parasite density and type of filter paper. For 3MM® Whatman filter paper, the sensitivity was 100%, 73%, and 93% for the TE, methanol, and Chelex® methods, respectively. For the longer stored 903® Schleicher & Schuell filter paper, the sensitivity was 93%, 73%, and 0%, respectively. This rapid, simple, and inexpensive extraction method generated superior results from archived specimens compared with the two standard methods and may represent a useful tool in molecular epidemiologic studies.

The aim of the study was to assess whether infections with Plasmodium falciparum isolates encoding the P. falciparum chloroquine resistance transporter (pfcrt) gene K76T polymorphism, a molecular marker for chloroquine resistance, are associated with multiple infections, age, or clinical signs of malaria in a semi-immune population in a holoendemic area of Burkina Faso. The parameters of interest were investigated in 210 P. falciparum-positive inhabitants. Logistic regression analysis showed that pfcrt K76T-carrying isolates are significantly more likely to cause anemia and splenomegaly. Furthermore, we found that infections with P. falciparum isolates encoding pfcrt K76T are dependent on age rather than multiple infections. Our findings suggest that pfcrt K76T might serve as a valuable marker for assessing the long-term clinical effect of chronic infections with chloroquine-resistant P. falciparum isolates in populations, without the need of drug efficacy trials.

Malaria incidence data at the district level from 1997 to 2002 and total malaria case data from 1965 to 2002 in Thailand were analyzed to determine the spatial and temporal dynamics of Plasmodium falciparum and P. vivax malaria incidence. Over the 37-year period, there was a 35-fold reduction in the incidence rates of P. falciparum malaria (11.86% in 1965 versus 0.34% in 2002) and a 7-fold reduction in P. vivax malaria (2.89% in 1965 versus 0.40% in 2002). The incidence ratio of P. falciparum to P. vivax malaria was reduced from 4.1 to 0.8 during this period. Malaria incidence rate exhibited the most rapid reduction between 1975 and 1985, coinciding with the introduction of a combination of antifolate drugs (sulfadoxine-pyrimethamine). The distribution maps of P. falciparum and P. vivax malaria incidence rates indicated a high spatial heterogeneity. The Thailand-Myanmar and Thailand-Cambodia border areas, where migration of foreign workers was pronounced, had the highest incidence rates for P. falciparum, P. vivax, and mixed-species infections. Transition probability analysis based on the malaria incidence rate among Thai residents indicated that there was an overall trend of decrease in the number of malaria cases and the number of high incidence districts between 1997 and 2002. High spatial variation in malaria incidence and local human migration patterns suggest that malaria control measures need to be adjusted according to local environmental and demographic settings.

While resistance to older antimalarials is increasingly common, newer antimalarials are still not widely available or affordable in much of Africa. Older antimalarials used in combination might be adequately effective in treating uncomplicated malaria. The objective of this study was to determine whether the combination of sulfadoxine-pyrimethamine (SP) and chloroquine (CQ) is superior to SP alone in the treatment of uncomplicated Plasmodium falciparum malaria in Nigerian patients. We recruited subjects with malaria, defined as the presence of fever and parasitemia > 2,000/μL, from the outpatient department of a Nigerian teaching hospital. We alternately assigned 280 subjects to receive SP with or without CQ. We assessed clinical and parasitologic responses on days 1, 2, 3, 7, and 14. A total of 114 in the SP + CQ group and 116 in the SP group completed the study. By day 3, 97 (75%) in the SP + CQ group and 52 (42%) in the SP group had cleared their parasitemia (P < 0.001); by day 14, 112 (98%) and 67 (58%), respectively, had cleared their parasitemia (P < 0.001). By day 3, 82 (63%) in the SP + CQ group and 20 (16%) in the SP group were symptom free (P < 0.001). When a modified World Health Organization clinical classification system was used, adequate clinical response occurred in 99 (87%) and 61 (53%) of those in the SP + CQ and SP groups, respectively. RI, RII, and RIII resistance to SP + CQ was 7.9%, 3.5%, and 1.8%, respectively, whereas resistance to SP was 23%, 17%, and 5%, respectively. Combined SP + CQ is superior to SP alone for treatment of uncomplicated malaria in Nigerian patients and may prolong the usefulness of these readily available and affordable drugs.

Folate antagonizes the antimalarial action of sulfadoxine-pyrimethamine (SP) in vitro, but its role in vivo is not well understood. We measured blood folate concentrations and SP therapeutic outcomes in Malawian children. Children with late treatment failure and those with adequate clinical and parasitologic responses had similar demographic characteristics, prevalence of parasite mutations conferring resistance to SP, and blood concentrations of anti-malarial drugs following treatment. However, a higher folate concentration was associated with late treatment failure. Patients from a low malaria transmission site had higher blood folate concentrations than those in a higher transmission site (mean ± SEM = 39 ± 9.3 ng/mL versus 29 ± 10 ng/mL; P < 0.0001), and there was a higher rate of late treatment failure in the low transmission area (54.4% versus 40.2%; P = 0.010). This study also provides the first evidence of the independent role of physiologic folate concentrations in in vivo SP therapeutic efficacy, and the critical role of pyrimethamine concentrations in the therapeutic efficacy of SP when one controls physiologic folate levels and the frequency of critical dihydrofolate reductase/dihydropteroate synthase mutations.

We monitored diel-landing periodicity (biting activity/cycle) of Ochlerotatus niveus and the infection/infectivity pattern through human-landing collections on Teressa Island, which is remotely located in the Nicobar district of the Andaman and Nicobar group of Islands of India, for a period of one year. The biting activity was seen throughout the day, exhibiting a bimodal peak, the first at dawn (4:00–6:00 am) and the other towards dusk (5:00–6:00 pm). This pattern was similar during all the seasons of the year. Peak biting hours of Oc. niveus coincides with the peak appearance of microfilariae. Overall infection and infectivity rates were 2.65% and 0.5%, respectively. Perennial transmission is evident from the records of vectors with parasites (infection), including infective larvae in all months of the year, although no infective mosquitoes were recorded at a few points. The risk of transmission of filariasis based on parity status of Oc. niveus was maximal at dusk (5:00–6:00 pm) in this region. The issue of control with respect to reducing human-vector contact is discussed.

The gold standard serodiagnostic assay for cysticercosis and neurocysticercosis, diseases caused by the metacestode of Taenia solium, uses lentil lectin-purified glycoprotein (LLGP) in a Western blot assay. We tested two antigens derived from LLGP, synthetic TS18var1 (sTS18var1) and recombinant GP50 antigen (rGP50), in an enzyme-linked immunosorbent assay (ELISA) using serum and cerebrospinal fluid (CSF) samples. The sensitivity for serum and CSF was 94.7% and 100% for rGP50 and 90.4% and 90.2% for sTS18var1, respectively. The specificity for serum and CSF samples was 93.8% and 100% for rGP50 and 90.3% and 98.0% for sTS18var1, respectively. The use of these antigens individually or combined as a diagnostic antigen cocktail eliminates the need for purification of antigens from parasite material and offers the advantage of using a simple and quantitative ELISA format.

There are two foci of alveolar echinococcosis (AE) caused by Echinococcus multilocularis in Japan. The first focus is on Rebun Island where AE patients were found from 1937, and the second is in eastern Hokkaido where patients have been found since the 1960s. The origin of the second focus is unknown. To further investigate AE in eastern Hokkaido, wild rodents (Muridae) were captured and examined for infection on Kunashiri Island, which is located 15 km off the northeastern coast of Hokkaido. Metacestodes of E. multilocularis were isolated from two of 31 voles, all of which were identified to be Clethrionomys rufocanus. Mitochondrial DNA sequencing data of recovered cestodes showed total identity with the cestode reported from Hokkaido. These results suggest that E. multilocularis may have been introduced to Hokkaido from Kunashiri Island during or after 1965.

Hydatid disease (echinococcosis) has a two-host cycle involving the domestic dog and grazing animals. Humans are also infected by the dog. Both unilocular (Echinococcus granulosus in yaks, sheep, and goats) and multilocular (alveolar) (E. multilocularis in hares and rodents) hydatids are common in western Sichuan in the People’s Republic of China. Humans and dogs are equally infected with both species. Many yaks (Bos grunniens) were found with multilocular cysts that visually were deemed to be E. multilocularis. However, a histologic and molecular study showed that they were actually E. granulosus. No infective cysts were found in 125 necropsied yaks. We conclude that the yak is an inadequate and dead-end host for the sheep dog (G1) strain of Echinococcus granulosus and also for E. multilocularis.

Albendazole is a benzimidazole with wide spectrum coverage as an antiparasitic drug. Reported side effects have been minimal. We report the case of a patient who died with severe prolonged pancytopenia beginning during the third week of therapy for a pulmonary echinococcal cyst. This case was a 68-year-old man who presented with a large cystic lung mass. His medical history was significant for Child-Pugh class B cirrhosis. A prolonged course of albendazole was initiated. Two weeks later, the patient presented in septic shock with severe pancytopenia. The patient was initially resuscitated, but died after 10 days with no marrow recovery. Autopsy was consistent with albendazole-induced pancytopenia. This is the third human case of pancytopenia and the first death reported in relation to albendazole-induced pancytopenia. Neutropenia seems to be related more to higher dosage and longer duration of use. Albendazole sulfoxide peak dose and half life are significantly prolonged by liver disease and concomitant administration of certain drugs. The severity and duration of albendazole-induced pancytopenia in this case was likely related to the underlying liver disease. Frequent serial monitoring of blood counts and cessation of medication with any evidence of marrow toxicity in such patients is warranted.

To determine the prevalence and risk factors for Toxoplasma gondii infection in Guatemalan children, in 1999 and 2003 we surveyed caretakers and serologically tested children in the San Juan Sacatepequez area using Platelia Toxo IgG TMB enzyme immunoassay kits. In 1999, of 532 children six months to two years old, 66 (12.4%) were antibody positive. In 2003, in 500 children 3–10 years old antibody prevalence increased from 24% to 43% at age five years then leveled off. By multivariate analysis, drinking well water (relative risk [RR] = 1.78, 95% confidence limit [CL] = 1.00, 3.17, P = 0.05) and not cleaning up cat feces (RR = 2.06, 95% CL = 1.00, 4.28, P = 0.05) increased the risk of T. gondii seropositivity. Most T. gondii infections in children from these villages occurred by age five, but half were still not infected by adolescence. Therefore, it is important to educate girls entering child-bearing age about the risks of acute T. gondii infection and the local risk factors for infection.

Direct data entry, using handheld computers, may simplify and streamline data management, especially in remote settings. We compared the accuracy of data entry using the current standard practice (a paper-based case report form with double data entry) with that using a personal digital assistant (PDA) in a clinical study in rural Gabon. The rate of discrepant entries was 1.7%. Categorical data (presented in “pull down” menus on the PDA) were more commonly discrepant than were continuous “typed in” data (2.4% versus 1.2%; P = 0.001). Both systems functioned smoothly and no data were lost. The clinicians involved in this study preferred the handheld computers, and their use will be considered in future studies in an African clinical research network.

Aedes aegypti, the mosquito responsible for transmitting dengue, has colonized many cities and towns throughout Arizona. Determining both the migration between, and the origin of, local Ae. aegypti populations is important for vector control and disease prevention purposes. Amplified fragment length polymorphism was used to infer geographic structure and local substructure, and effective migration rates (M, migrants per generation) between populations, and to determine genetic differentiation between populations (ΦPT). Three geographically and genetically differentiated groups of populations were identified. Population substructure was only detected in the border town of Nogales. Reliable estimates of M between regions ranged from 1.02 to 3.41 and between cities within regions from 1.66 to 4.44. In general, pairwise ΦPT were lowest between cities within regions. The observed patterns of genetic differentiation suggest infrequent migration between populations and are compatible with the idea of human transport facilitating dispersal between regions.

Up to 75% of women with urinary schistosomiasis have Schistosoma haematobium ova in the genitals. This study aimed to describe the prevalence of gynecologic S. haematobium infection and to differentiate the disease from sexually transmitted infections (STIs). Gynecologic and laboratory investigations for S. haematobium and STIs were performed in 527 women between the ages of 20 and 49 in rural Zimbabwe. Genital homogenous yellow and/or grainy sandy patches, the commonest type of genital pathology, were identified in 243 (46%) women. Grainy sandy patches were significantly associated with S. haematobium ova only. Genital S. haematobium ova was also significantly associated with homogenous yellow sandy patches, mucosal bleeding, and abnormal blood vessels. The presence of ova was not a predictor for ulcers, papillomata, leukoplakia, polyps, or cell atypia. Mucosal sandy patches seem to be pathognomonic for S. haematobium infection in the female genitals. Coexistence of ova and other lesions may not be causal.

Adult hamsters that survived experimental West Nile virus (WNV) infection developed persistent viruria. Infectious WNV could be cultured from their urine for up to 52 days. Immunohistochemical examination of kidneys of viruric animals showed foci of WNV antigen in renal tubular epithelial and vascular endothelial cells. These findings are compatible with virus replication and persistent infection of renal epithelial cells. The potential clinical and virologic significance of these findings as well as their possible epidemiologic importance are discussed.

The results of experiments comparing the pathogenesis of West Nile virus (WNV) following infection by mosquito bite, needle inoculation, and ingestion are reported. Adult hamsters were readily infected by all three routes. The level and duration of viremia, clinical manifestations, pathology, and antibody response in the hamsters following mosquito infection and needle inoculation were similar; after oral infection, the onset of viremia was delayed and the mortality was lower, but the level and duration of viremia, histopathology, and antibody response were similar to the other routes. The results from this and previously published studies indicate that a wide variety of animal species are susceptible to oral infection with WNV and that orally infected animals develop a viremia and illness similar to that following the bite of infected mosquitoes. Oral infection appears to be an alternative transmission mechanism used by a number of different flaviviruses; its potential role in the natural history of WNV is discussed.

Epizootic strains of Venezuelan equine encephalitis virus (VEEV) cause epidemics by exploiting equines as highly efficient amplification hosts for mosquito transmission. Although phylogenetic studies indicate that epizootic VEEV strains emerge via mutation from enzootic progenitors that are incapable of efficient equine amplification, the molecular mechanism(s) involved remain enigmatic. The convergent evolution of E2 envelope glycoprotein mutations suggests that they are critical to VEEV emergence, but little is known about the role of non-envelope genes. We used the guinea pig, the small animal model that best predicts the ability to generate equine viremia, to assess the role of envelope versus other mutations in the epizootic phenotype. Using reciprocal chimeric viruses generated by swapping the envelope genes of closely related epizootic IC and enzootic ID strains, infections of guinea pigs demonstrated that envelope and non-envelope genes and sequences both contributed to virulence. However, early replication in lymphoid tissues appeared to be primarily envelope dependent.