Role of habitat components on the dynamics of Aedes albopictus (Diptera: Culicidae) from New Orleans.

Monthly sampling of tire pile populations of Aedes albopictus (Skuse) in Orleans Parish, New Orleans, LA, was done in 1995 to determine prevalence of ascogregarine parasites and changes in wing length. Prevalence of Ascogregarina taiwanensis (Lien & Levine) infection was 100% in midsummer and decreased in the fall and spring (60-70%). Wing lengths were longest in the spring and fall and shortest in midsummer. We evaluated the effect of A. taiwanensis infections under high and deficient levels of leaf litter nutrients on mortality, development time, wing length, and reproductive potential of a New Orleans strain of Ae. albopictus. Parasitism and deficient nutrients caused a 35% increase in the rate of larval mortality and significantly extended the development time of females. Parasitized adults were 5% smaller and produced 23% fewer eggs than unparasitized siblings. In addition, abnormal Malpighian tubule morphology and melanization of ascogregarines were seen in adults from nutrient-deficient microcosms. We conclude that ascogregarine infections affect the dynamics of Ae. albopictus by increasing the mortality of immature stages when nutrients supplies are scarce, and by decreasing the reproductive capacity of females under high nutrient conditions.

Effect of nutrient levels and Ascogregarina taiwanensis (Apicomplexa: Lecudinidae) infections on the vector competence of Aedes albopictus (Diptera: Culicidae) for Dirofilaria immitis (Filarioidea: Onchocercidae).

The effect of habitat nutrients and Ascogregarina taiwanensis (Lein & Levine) infection on the vector competence of a New Orleans strain of Aedes albopictus (Skuse) for Dirofilaria immitis (Leidy) were evaluated. Larvae were infected with A. taiwanensis oocysts and reared under high and deficient nutrient conditions using leaf litter as a food source. Ascogregarine-infected and uninfected females were fed on D. immitis-infected blood and examined after 15 d for filariae. Susceptibility to infection with filaria was 60-70% for all females. In groups reared under high nutrients, the infective rate (3rd-stage larvae present) of coinfected females (18%) was significantly greater than females infected only with heartworm (6%). Host mortality following blood meals was significantly less in coinfected (22%) than in heartworm-infected females (37%). Under deficient nutrient conditions, there was no significant difference between the infective rate (8%) or post-blood meal mortality (5%) of coinfected females compared with heartworm-infected females. Prevalence of melanization reactions in coinfected females was significantly higher (31%) than in females infected only with heartworm (6%) at both nutrient levels. It is concluded that high nutrient levels and ascogregarine infection increase the vector competence of Ae. albopictus for D. immitis by enhancing the immune response so that fewer filariae develop, causing lower host mortality. Under low nutrient conditions, the smaller host contains less food reserves for filariae development, and in coinfected females melanization reactions and damage to the Malpighian tubules may reduce vector survival.

Correlations between intestinal parasitosis, physical growth, and psychomotor development among infants and children from rural Nicaragua.

The correlations between malnutrition, parasitosis (especially helminth infections), and child development are complex, and studies of these interrelationships will allow health agencies to maximize screening and intervention strategies for developing countries. We examined these correlations in a cross-sectional program in Carazo State, Nicaragua. Nine hundred sixty-one children in two age strata (ages 0-24 months and ages 2-10 years) from one urban and three rural communities were screened for intestinal parasites (direct smear and ZnSO4 flotation), malnutrition, and developmental delays. Nutritional status was determined as weight-for-age (WFA), weight-for-height (WFH), and height-for-age (HFA). Developmental status (normal, suspect) was determined for the four subtests of the Denver II Screening Test. The prevalence of malnutrition was 14.6% (WFA), 8.4% (WFH), and 36.3% (HFA). Parasitosis was more prevalent in children less than 24 months of age with low HFA, whereas in older children low WFA was more closely associated with parasitic infections. Ascaris and Trichuris were more prevalent in malnourished children. On the Denver II, suspect test results in all four categories (language, social, gross motor, and fine motor) were associated with low WFA, and suspect language tests were associated with both intestinal parasites (P = 0.0003) and Ascaris infection in particular (P = 0.044). Developmental disabilities are a significant and frequently undetected health problem in developing countries, and malnutrition associated with intestinal helminth infections may be an important contributory factor for these disabilities.

PIP: Studies of the correlations between malnutrition, parasitosis, and child development will help health agencies to maximize screening and intervention strategies for developing countries. Such correlations were examined in a cross-sectional study in Carazo State, Nicaragua. 961 children aged 0-24 months and 2-10 years from 1 urban and 3 rural communities were screened for infection with intestinal parasites, malnutrition, and developmental delays. Developmental status was determined for the 4 subtests of the Denver II Screening Test. The prevalence of malnutrition was 14.6% according to weight-for-age (WFA), 8.4% for weight-for-height (WFH), and 36.3% for height-for-age (HFA). Parasitosis was more prevalent among children under age 2 years with low HFA, while low WFA was more closely associated with parasitic infections in older children. Ascaris and Trichuris were more prevalent in malnourished children. On the Denver II, suspect test results in language, social, gross motor, and fine motor were associated with low WFA, while suspect language tests were associated with both intestinal parasites, and Ascaris infection in particular. Developmental disabilities are a significant and often undetected health problem in developing countries. Malnutrition associated with intestinal helminth infections may be an important contributory factor for such disabilities.

Country-wide prevalence of Ascogregarina culicis (apicomplexa: lecudinidae), a protozoan parasite of Aedes aegypti in Trinidad, West Indies.

The prevalence of the gregarine parasite Ascogregarina culicis was determined for Aedes aegypti populations in Trinidad, West Indies. Over 5 months, a total of 5,651 Ae. aegypti larvae were collected and identified from 419 sites throughout Trinidad as part of a national dengue surveillance program. Ascogregarina culicis infections were detected in 13.4% of 1,986 Ae. aegypti larvae dissected. In 7 of 8 counties or major subdivisions where this parasite was detected in Trinidad, the prevalence per locality ranged from 9.6 to 17.1% with an associated parasite density of 19.1-51.9 trophozoites/larva. Confirming that Ae. aegypti populations in Trinidad are highly susceptible to infection with A. culicis parasites, experimental studies showed that a strain of A. culicis from Florida readily infected 3 strains of Ae. aegypti from Trinidad with essentially no associated mortality. This report extends the known geographic range of A. culicis in Ae. aegypti populations and represents one of the first country-wide surveys for this gregarine parasite.

Country-wide prevalence of Ascogregarina culicis ( apicomplexa: lecudinidae), a protozoan parasite of Aedes aegypti in Trinidad, West Indies

The prevalence of the gregarine parasite Ascogregarina culicis was determined for Aedes aegypti populations in Trinidad, West Indies. Over 5 months, a total of 5,651 Ae. aegypti larvae were collected and identified from 419 sites throughout Trinidad as part of a national dengue surveillance program. Ascogregarina culicis infections were detected in 13.4 percent of 1,986 Ae. aegypti larvae dissected. In 7 of 8 counties of major subdivisions where the parasite was detected in Trinidad, the prevalence per locality ranged from 9.6 to 17. 1 percent with an associated parasite density of 19.1-51.9 trophozoites/larva. Confirming that Ae. aegypti populations in Trinidad are highly susceptible to infection with A. culicis parasites, experimental studies showed that a strain A. culicis from Florida readily infected 3 strains of Ae. aegypti from Trinidad with essentially no associated mortality. This report extends the known geographic range of A. culicis in Ae. aegypti populations and represents one of the first country-wide surveys for this gregarine parasite. (Au)

Dirofilaria (Filarioidea: Onchocercidae) infection in Aedes albopictus (Diptera: Culicidae) collected in Louisiana.

First-stage Dirofilaria larvae were found infecting the Malpighian tubules in 3 of 163 Aedes albopictus collected from New Orleans, LA, during June-July 1994. Further studies will be necessary to provide definitive identification of the parasite species, and to better describe the vectorial status of Ae. albopictus.