Transmission of Plasmodium vivax malaria in San Diego County, California, 1986.

Between 18 June and 20 September 1986, 28 cases of Plasmodium vivax malaria were documented in Carlsbad, California, a coastal town north of San Diego. Malaria occurred in 1 local resident who had no risk factors, a second local resident who had traveled to a malarious area 9 months earlier, and 26 Mexican migrant workers (MWs). Among the 28 cases, 27 lived in a square mile marshy area where Anopheles hermsi, a newly described American species of the Anopheles maculipennis group, was known to be breeding. An investigation of MWs residing in the affected area was done to determine the extent of the outbreak and to identify risk factors for acquiring malaria. We interviewed and drew blood from 304 healthy MWs and 17 (65%) of the MWs with malaria. Fluorescent antibody titers to P. vivax greater than or equal to 1:256 occurred in 14 (82%) of the 17 MWs with malaria tested and 9 (3%) of the healthy MWs. The principal risk factor identified for contracting malaria was sleeping outside on a hillside adjacent to the marshy area. Malaria in a local resident with no malaria risk factors and the clustering in time and place of 26 cases suggest that P. vivax malaria was introduced and local transmission was sustained through several generations, producing the largest outbreak of introduced malaria in the United States since 1952.

Comparison of heterologous adult Brugia malayi and homologous Onchocerca volvulus antigen in the enzyme-linked immunosorbent assay (ELISA) for Guatemalan onchocerciasis.

To determine the susceptibility of a heterologous filarial antigen for measuring Onchocerca volvulus antibodies, worms were compared using an enzyme-linked immunosorbent assay (ELISA) test. Control serum samples from helminth-free U.S. residents and from helminth-infected but filariae-free Salvadoran residents were tested and compared with serum obtained from microfilariae-positive and -negative Guatemalan residents living in an area of endemic onchocerciasis. The results showed that none of the sera from U.S. residents had positive O. volvulus ELISA titers (greater than or equal to 1:160); however, 8.51% (4/47) had positive B. malayi ELISA titers (greater than or equal to 1:640). The geometric mean titers with the B. malayi ELISA test were higher than with the O. volvulus ELISA test--in sera from 47 U.S. residents (1:219 vs. 1:49), from 108 Salvadoran residents (1:92 vs. 1:71), and from 145 microfilariae-negative (1:539 vs. 1:167) and 303 microfilariae-positive (1:1,270 vs. 1:561) Guatemalan residents. The B. malayi ELISA test exhibited slightly less sensitivity than the homologous O. volvulus ELISA test; nevertheless, a good correlation (r = 0.74) was found between the 2 test antigens, indicating that the B. malayi antigen could be used to measure O. volvulus antibodies.

Diagnosis of Onchocerca volvulus infection in Guatemalan children.

Nodule examination, the Mazzotti test (a provocative challenge with diethylcarbamazine), and the enzyme-linked immunosorbent assay (ELISA) were compared for diagnostic efficacy in children who were born in an area endemic for onchocerciasis in Guatemala and were skin-biopsy negative for microfilaria of Onchocerca volvulus. Four groups of children under 16 years of age were formed based upon the possible combinations of nodule positivity or negativity and ELISA positivity or negativity. Only those children with a positive (greater than or equal to 1:160) ELISA titer had a positive Mazzotti test (9 of 20 tested), regardless of the presence or absence of nodules. These results suggest that the current ELISA serology is highly sensitive for low density infections, and should be considered in surveys for the incidence of new Onchocerca infections.

Studies on the Indochina I/CDC strain of Plasmodium falciparum in Colombian and Bolivian Aotus monkeys and different anophelines.

The Indochina I/CDC strain of Plasmodium falciparum was isolated from a physician returning to the United States after working in the refugee camps along the Thailand-Kampuchean border. The strain was established in splenectomized Aotus monkeys from Colombia after being grown in vitro for 50 days. During the first three passages in Colombian monkeys, the parasites were not infective to Bolivian Aotus monkeys. After six intervening passages in Saimiri sciureus monkeys, the parasites produced high parasitemias in both Colombian and Bolivian Aotus, but gametocytes were no longer produced. Mosquito infections were obtained only during the first three passages in the Colombian monkeys. The most susceptible mosquito was Anopheles freeborni, followed by An. dirus, An. stephensi, An. maculatus, An. culicifacies, and, rarely, An. gambiae. Sporozoites were found in the salivary glands of the An. freeborni, An. dirus, An. stephensi, and An. maculatus.

Early formation of the nodule in Guatemalan onchocerciasis.

Thirty-eight nodules containing adults of Onchocerca volvulus were removed from 36 patients who had no detectable microfilariae in skin snips. Worms were digested from nodules in collagenase solution, maintained alive in vitro, and the number, sex, and state of fecundity were recorded. A total of 48 female and 8 male worms were recovered; 39 females were in the nodules without the presence of a male. Eleven females (22.9%) had microfilariae in utero or produced microfilariae in vitro; seven of these were found together with males in the nodules while four were not. No nodules were found around male worms unless a female was also present. These observations indicate that the nodule forms only around female worms and that mating probably occurs before or early during nodule formation. Furthermore, the production of microfilariae by the the female is not essential for nodule formation since many nodules contained non-fecund, living females.

Assessment of chloroquine sensitivity of Plasmodium falciparum in Choluteca, Honduras.

During an outbreak of urban malaria in Choluteca, Honduras, the response of local isolates of Plasmodium falciparum to chloroquine was assessed. The 7-day WHO alternative standard field test was used together with three in vitro tests: the Rieckmann macro- and micromethods and a new 48-hour test which underwent its first field trial in this study. No chloroquine resistance was found in in vivo tests in 10 patients or in the in vitro tests on blood samples from 6 patients.

Serologic studies on onchocerciasis in Guatemala using fixed-tissue sections of adult Onchocerca volvulus.

Sera from 458 residents of a coffee plantation in an area of Guatemala endemic for onchocerciasis were examined for the presence of antibodies to Onchocerca volvulus using a fluorescent antibody (IFA) test with sections of adult worms as the antigen. Antibody response increased with age of the residents and microfilarial density. A total of 70.0% of the residents were serologically positive and 65.1% were positive for microfilariae. Males had higher microfilarial densities and higher IFA responses. Sixty-three individuals were positive for microfilariae and IFA-negative indicating a lack of sensitivity on the part of the test antigen. Seventy-four individuals were negative for microfilariae and IFA-positive, suggesting the possible usefulness of the test in the determination of present or past infection in the absence of microfilariae.

Seroepidemiological studies of malaria in pregnant women and newborns from coastal El Salvador.

A cohort of 113 women and their newborns from the coastal area of El Salvador were studied longitudinally to estimate malaria incidence and indirect fluorescent antibody (IFA) response to malaria infection. The district in which the study was conducted had an estimated annual parasite index of 600/1,000 inhabitants, and all malaria infections were treated immediately with a 4-aminoquinoline. In the third trimester of pregnancy, the IFA response to Plasmodium falciparum was significantly depressed. As a result of antimalarial therapy and depressed immune responsiveness, 49% (P. vivax) and 53% (P. falciparum) of the pregnant subjects had a malaria IFA titer less than 1:20 at the time of delivery. Malaria IFA crossed the placenta to the fetus with a step-down of approximately a 4-fold dilution, except for the step-up noted in the P. falciparum titer for 17 of 116 newborns. Due to the overall low prevalence and intensity of maternal IFA, a titer of at least 1:20 was passed to only 23% (P. vivax) and 45% (P. falciparum) of newborns. Passively-acquired malaria IFA degraded with a half-life estimated between 43 and 52 days. During follow-up of infants to 6 months of age, no protection from malaria resulting from passively-acquired antibody could be demonstrated. Because of the limited transplacental immunization of these newborns with antimalarial antibody, it appears that passive immunity can exert little effect on the incidence of infant malaria in coastal El Salvador.

An apparent outbreak of rickettsial illness in Costa Rica, 1974.

A focal outbreak of highly fatal disease occurred in eastern Costa Rica in 1974. No rickettsial spotted fevers have previously been reported in Costa Rica. Nevertheless, the available evidence points to an unidentified rickettsial pathogen, probably of the spotted fever group, as the agent responsible for this outbreak.

Disease-surveillance and decision-making after the 1976 Guatemala earthquake.

In the first 3 weeks after the 1976 earthquake in Guatemala a system for collecting, analysing, and disseminating information of medical importance was instituted in the disaster area. Data on cases of selected diseases, number of available hospital beds, and medical supplies were collected, and reported epidemics were investigated. The system functioned well despite the limited numbers of trained personnel. Collection and analysis were quick enough for data to be used immediately in decision-making. No epidemics of communicable diseases were observed in the affected area. The number of dog bites in Guatemala City increased but no cases of rabies were reported. The success of the surveillance system in Guatemala suggests that immediate use of epidemiological methods should be an integral part of disaster relief.

Amino acid synthetic media for fungal pathogens based on aminopeptidase specificities: Histoplasma capsulatum, Blastomyces dermititidis, Paracoccidioides brasiliensis and Cryptococcus neoformans.

The development of simple and chemically defined liquid media for Histoplasma capsulatum, Blastomyces dermatitidis, Paracoccidioides brasiliensis and Crypto-occus neoformans according to their aminopeptidases profiles as amino acid requirement was described. When 1.5% purified agar was added, these media also supported excellent mycelial growth and sporulation of the deep mycoses. H. capsulatum was converted to and maintained in yeast phase when 0.1% L-cystine was added to the solid medium incubated at 37 degrees C.