Anthropometric nutrition status and diarrhea prevalence in children in El Salvador.

Data are presented to quantify the relationship between nutritional status and diarrheal disease reported in a 1-week period in children in El Salvador. A strong association was observed between reported diarrhea and combined wasting (defined by low weight-for-height) and stunting (defined by low height-for-age). This association held for all age groups studied and was consistently observed in the seasons of low and high prevalence of malnutrition. There were also significant associations between reported diarrhea and wasting alone, low weight-for-age, and low arm circumference. No consistent association was observed between reported diarrhea and stunting or chronic undernutrition as defined by low height-for-age, suggesting that short stature is not, by itself, a risk factor for diarrhea. Previously defined seasonal patterns of malnutrition for El Salvador as a whole were confirmed and appear to affect some geographic subregions more severely than others. Definition of these regional and seasonal patterns of malnutrition and their association with diarrhea has implications for the targeting and timing of nutrition interventions.

Antibody responses to malarial antigens in the Wopkaimin population of the Star Mountains, Papua New Guinea.

Antibody responses to malarial antigens were determined in 614 serum samples collected from the Wopkaimin population of the Star Mountains of Papua New Guinea. In point prevalence surveys made in 1982-1983, 33.7% of the persons examined were infected with Plasmodium falciparum, P. vivax, or P. malariae. Of these, 72.9% were infected with P. falciparum. In a standard fluorescent antibody test, highest level responses were to P. falciparum, followed by P. malariae, P. vivax, and P. ovale. A strong correlation was found between results of the fluorescent antibody tests and those obtained in an enzyme-linked immunosorbent assay using P. falciparum antigens. The failure of immune responses to eliminate these species of Plasmodium in this highly isolated population is discussed.

Antibody response to heterologous and homologous antigens in Brugia malayi- and B. pahangi-infected Mongolian jirds as measured by the enzyme-linked immunosorbent assay (ELISA).

Sequentially collected sera from Mongolian jirds (Meriones unguiculatus) infected with Brugia malayi and B. pahangi were tested for antibodies to homologous and heterologous antigens by the enzyme-linked immunosorbent assay (ELISA). Titers were less than 1:100 prior to infection and rose rapidly (within 2 weeks). Peak titers were observed prior to patent microfilaremia, and high titers persisted during infection. Use of the homologous antigen did not increase sensitivity or specificity of the ELISA. In fact, B. malayi-infected jirds demonstrated higher titers to the heterologous antigen, B. pahangi, than to the homologous antigen. Fractionation of B. malayi antigen over a wide pH range using isoelectric focusing did not eliminate cross-reactions, but the reactions of 20 B. malayi sera and 20 B. pahangi sera tested more strongly to specific fractions, particularly in the lower pH range.

The enzyme-linked immunosorbent assay (ELISA) for malaria. III. Antibody response in documented Plasmodium falciparum infections.

Serum specimens from patients in El Salvador, Central America, with slide-proven Plasmodium falciparum infections were examined for antibodies to P. falciparum using the enzyme-linked immunosorbent assay (ELISA) and the indirect fluorescent antibody (IFA) methods. Both serologic tests were positive in 78.1% of the 827 samples, both negative in 5.4%, the ELISA positive alone in 6.3%, and the IFA alone in 10.2%. Agreement between the serologic tests was better in the specimens with high positive titers (high IFA = high ELISA). Seropositivity rates and geometric mean titers were higher in the older (greater than or equal to 15 years) age groups for both ELISA and IFA; in such persons, the IFA was positive in 92% and the ELISA in 88%. The lowest seropositivity rates found by the ELISA were observed in children; 27.6% of 98 children less than or equal to 4 years of age were negative. A longer duration of infection as evidenced by the presence of gametocytes on the blood slide resulted in higher positivity rates by both ELISA and IFA. This phenomenon, particularly apparent in young children, supports the belief that the more important variable in determining the proportion of false negatives is previous malaria experience and not age. The results indicate that, while neither serologic test is appropriate as a diagnostic aid, both the ELISA and the IFA would be useful in epidemiologic investigations.

Observations on the infectivity of two strains of Plasmodium vivax from Vietnamese refugees to Aotus monkeys and anopheline mosquitoes.

Two strains of Plasmodium vivax (NAM and ONG) were isolated from Vietnamese refugees and established in splenectomized Aotus monkeys from Colombia and Bolivia. Mosquito infections were readily obtained from animals with no prior malarial experience or with a history of infection with P. falciparum only. Those animals with previous infections with P. vivax supported only low parasitemias, and the mosquito infections were minimal. Complete development of the sporogonic cycle was obtained with all species of mosquitoes tested. The most susceptible mosquito was An. dirus. Other mosquitoes readily infected with these strains were An. culicifacies, An. maculatus, An. gambiae, An. stephensi, and the two North American species, An. freeborni and An. quadrimaculatus. Transmission from one monkey to another was obtained via the bites of infected An. dirus, An. stephensi, and An. maculatus mosquitoes.

Observations on two strains of plasmodium falciparum from Haiti in Aotus monkeys.

Two strains of Plasmodium falciparum originating in Haiti were studied in the Aotus monkey. The Haitian I/CDC strain was first adapted to in vitro cultivation and subsequently inoculated into monkeys. The Haitian III/CDC strain was inoculated directly from a human patient into the Aotus monkey. The strains varied in their levels of pathogenicity to the animals. The Haitian I/CDC strain was highly virulent in six splenectomized animals; in one intact animal, the infection could be controlled but not eliminated with periodic doses of quinine and chloroquine. After subsequent splenectomy, the animal developed high parasitemias and died. No gametocytes developed in any of the Haitian I infections. The Haitian III strain was lethal to five of the 14 splenectomized monkeys inoculated, but some were able to control their infections without drug intervention. Gametocytes developed in all infections that persisted for an adequate length of time, and infections of mosquitoes were obtained both during the primary attack and the first recrudescence of the parasitemia. Of the mosquitoes tested, Anopheles freeborni was most susceptible to infection, followed by An. culicifacies, An. dirus, An. maculatus, and An. albimanus. The Haitian III strain was successfully transmitted to four other splenectomized Aotus monkeys via sporozoite inoculation using An. freeborni.

Development of Plasmodium inui in the Aotus trivirgatus monkey.

Four splenectomized Aotus trivirgatus griseimembra monkeys were affected with the OS strain of Plasmodium inui, a parasite of Old World macaques. High parasite densities were obtained and two of the animals died. Surviving animals maintained low to moderate level of chronic infections. Three of the four animals produced parasitemias which infected Anopheles dirus mosquitoes; oocyst densities were very low, however.

Studies on the Cambodian I strain of Plasmodium falciparum in Aotus monkeys.

The Cambodian I strain of Plasmodium falciparum, originally from Kampuchea was adapted for development in three different types of Aotus monkeys. High-level parasitemias were readily produced in splenectomized Colombian A. trivirgatus griseimembra monkeys. Initially, only minimal parasitemias developed in A. t. trivirgatus monkeys from Colombia. However, in one animal, adaptation occurred and high-level parasitemias were obtained during the second recrudescence of the infection. Passage to other A. t. trivirgatus monkeys indicated that the parasite was well adapted for development in splenectomized animals; low to moderate parasitemias were still produced in intact animals. This line of the parasite produced high level parasitemias when inoculated into splenectomized Aotus monkeys from Peru. Infections in Anopheles freeborni mosquitoes were obtained as late as the 7th passage in A. t. griseimembra monkeys and as late as the 7th recrudescence of the infection in an individual monkey (348 days after inoculation). The sporogonic cycle was completed in An. freeborni mosquitoes, and one transmission to an A. t. griseimembra monkey via the bites of infected mosquitoes was obtained.

Infection and transmission studies with the N-3 strain of Plasmodium fieldi in the Macaca mulatta monkey.

Seven different anophelines--Anopheles freeborni, An. dirus, An. maculatus, An. atroparvus, An. stephensi, An. albimanus, and An. quadrimaculatus--were shown to be susceptible to infection with the N-3 strain of Plasmodium fieldi. Transmission was obtained via the bites of An. dirus, An. stephensi, and An. maculatus mosquitoes to Macaca mulatta monkeys. Sporozoites dissected from An. freeborni were also shown to be infectious. Anopheles dirus and An. stephensi were the most suitable mosquitoes for transmission studies. Prepatent periods in M. mulatta monkeys following sporozoite inoculation ranged from 9 to 18 days with a mean of 12.3 days. Maximum parasitemias in intact animals following sporozoite inoculation ranged from 5,460 to 32,800 per mm3. Mean maximum parasitemia in splenectomized monkeys inoculated with parasitized blood was 146,000 per mm3.

Studies on a newly isolated strain of Plasmodium brasilianum in Aotus and Saimiri monkeys and different anophelines.

A strain of Plasmodium brasilianum was isolated from an Aotus vociferans monkey from Peru. The parasite readily infected Aotus monkeys from Bolivia and Columbia and Saimiri sciureus monkeys from Peru and Bolivia. Highest level mosquito infections were obtained by feeding on the Saimiri monkeys. The most susceptible mosquito was Anopheles freeborni, followed by Anopheles dirus, Anopheles stephensi, Anopheles gambiae, Anopheles culicifacies, Anopheles maculatus and Anopheles albimanus. Anopheles quadrimaculatus were also susceptible to infection. Degenerating oocysts were observed in An. dirus mosquitoes infected with this parasite. Transmission via the bites of infected An. maculatus mosquitoes was obtained to 3 Bolivian Saimiri monkeys; prepatent periods were 27, 27, and 29 days.

Studies of comparative infectivity of fifteen strains of Plasmodium vivax to laboratory-reared anopheline mosquitoes, with special reference to Anopheles culicifacies.

The Sattoki strain of species A of the taxon Anopheles culicifacies Giles was infected with 15 different strains of Plasmodium vivax from Asia, New Guinea, and Central and South America. A comparison of the relative infectivity indicated a marked variation for the different strains of P. vivax when compared to Anopheles freeborni mosquitoes.

Infection of Aotus azarae boliviensis monkeys with different strains of Plasmodium falciparum.

Eleven strains of Plasmodium falciparum from Asia, Africa, and Central America were inoculated into a total of 58 splenectomized Aotus azarae boliviensis monkeys. Eight of the strains produced high-level parasitemias, whereas 3 (2 from Honduras and 1 from Zaire) produced only low-level parasitemias. Mosquito infections were only obtained during the first 2 linear passages of the Santa Lucia strain from El Salvador. The results indicate that this species of Aotus monkey is highly susceptible to infection with strains of P. falciparum from different geographic areas, and therefore may be useful for a number of chemotherapeutic or immunologic studies. Its usefulness for mosquito infection studies is very limited.

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.

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.

Sporozoite-induced infections of the Salvador I strain of Plasmodium vivax in Saimiri sciureus boliviensis monkeys.

Twenty Saimiri sciureus boliviensis monkeys from Bolivia were inoculated intravenously with sporozoites of the Salvador I strain of Plasmodium vivax. All animals were splenectomized 7 days after inoculation. Inoculation of 100,000 sporozoites resulted in prepatent periods averaging 16.6 days; all monkeys developed high-level parasitemias with an average maximum of 103,000 per mm3. Inoculation of 10,000 sporozoites resulted in average prepatent periods of 19.4 days; one of the resulting infections produced a transient low-level parasitemia. Of 5 monkeys inoculated with 1,000 sporozoites, 4 had prepatent periods of from 24 to 35 days and 1 failed to demonstrate any parasitemia; 1 monkey supported a low-level transient parasitemia, whereas the other 3 monkeys had high-level parasitemias. It is proposed that by using a minimum inoculum of 10,000 sporozoites, the model system may be useful in the testing of anti-sporozoite vaccines directed against P. vivax.

The Uganda I/CDC strain of Plasmodium malariae in Aotus lemurinus griseimembra monkeys.

Two lines of the Uganda I/CDC strain of Plasmodium malariae were studied in splenectomized Aotus lemurinus griseimembra monkeys. A line initially adapted to these monkeys from an infected chimpanzee failed to produce high-level parasite counts or mosquito infection in 13 of this type of monkey during 16 linear passages. Another line, originally adapted from the chimpanzee to Aotus azarae boliviensis, after 7 linear passages in 3 different types of Aotus was then passaged to 14 splenectomized A. lemurinus griseimembra. Geometric mean maximum parasitemia in these monkeys was 18,400/mm3. Mosquito infections were readily obtained during the period just after the parasite count rose above 1,000/mm3. Anopheles freeborni, An. stephensi, An. dirus, and 2 strains of An. gambiae supported the development of the parasite to the presence of sporozoites in the salivary glands. Two attempts to transmit the strain to other splenectomized A. lemurinus griseimembra by sporozoite inoculation were unsuccessful.

Results of a nationwide proficiency test for carcinoembryonic antigen.

A proficiency testing survey for carcinoembryonic antigen (CEA) was conducted by the Center for Disease Control. The results from 125 laboratories throughout the United States indicate that many laboratories perform satisfactorily, but some laboratories need substantial improvement. Failure to follow manufacturer's recommendations and failure to heed the indications of "out of control" control results were two of the reasons for poor performance. Results reported for samples with CEA levels of larger than or equal to 20 ng/ml showed that the direct method produced significantly higher values than the indirect method on either whole of diluted plasma. Almost one-fourth of the results reported in this survey were placed in the wrong nominal group. It was determined that the results were log normally distributed and, consequently, that statistical methods that are appropriate for this distribtuion should be used for the analysis of CEA results. Most of the variation observed was the result of poor comparability between laboratories rather than lack of precision within the laboratory. This indicates that better performance could be achieved by better standardization and closer adherence to established procedures.

Comparison of kinetic and end-point diffusion methods for quantitating human serum immunoglobulins.

Proficiency testing results were used to compare the kinetic and end-point versions of the single radial immunodiffusion method for quantitating human serum immunoglobulins. Statistical analysis of the results indicated that the results were not normally distributed but that the log normal distribution gives the best fit of any of the well-known frequency distributions. Consequently, statistical analysis of immunoglobulin results must be log transformed before parametric statistical tests can be appropriately applied. In general, there were no significant differences in level, precision, or interlaboratory comparability for these two methods. However, levels were different for participants using Hyland reagents, and better interlaboratory comparability was achieved by the end-point assay for immunoglobulin M. There were no significant differences in reported levels when compared by manufacturer within the same method.