Development of sporogonic cycle of Plasmodium vivax in experimentally infected Anopheles albimanus mosquitoes

The sporogonic cycle of Plasmodium vivax was established and maintained under laboratory conditions in two different strains of Anopheles albimanus mosquitoes using as a parasite source blood from human patients or from Aotus monkeys infected with the VCC-2 P.vivax colombian isolate. Both the Tecojate strain isolate from Guatemala and the Cartagena strain from the colombian Pacific coast were susceptible to infections with P.vivax. A higher percentage of Cartagena mosquitoes was infected per trial, however the Tecojate strain developed higher sporozoite loads. Intravenous inoculation of Aotus monkeys with sporozoites obtained from both anopheline strains resulted in successful blood infections. Animals infected with sporozoites from the Tecojate strain presented a patent period of 21-32 days whereas parasitemia appeared between days 19-53 in monkeys infected with sporozites from Cartagena strain.

Development of a collection of bacteria causing meningitis in Rio de Janeiro from 1990 to 1991

From March 1990 to December 1992, the National Institute for Quality Control of Health-INCQS Research Collection received 1476 bacterial samples isolated from human cerebrospinal fluid of patients suspect of meningitis in Rio de Janeiro, from the São Sebastião State Institute of Infectious Diseases (IEISS). Neisseria meningitidis was found in most of these materials, followed in smaller number by Haemophilus sp. and Streptococcus pneumoniae. The great majority of N. meningitidis strains was serogroup B, followed by serogroup C and a few strains of serogroup W135. More than 50 of the isolated bacterial agents came from the predominant 0-4 years age group. The majority of the strains were from patients in the region known as "Baixada Fluminense" (Low Lands). The aim of the work presented here is to obtain samples of meningitis cases in at least 70 of the State of Rio de Janeiro and develop a collaborative research between INCQS-FIOCRUZ and the IEISS, in order to set up a collection of strains for future studies. However, despite work being carried out in a rather satisfactory way, difficulties still arise and have to be overcome, to survey data.

Development of a cyanobacterial biolarvicide

Results of studies on a larvicidal cyanobacterium that expresses a Bti cryIVD gene fusion are reported. Genetically altered Agmenellum quadruplicatum PR-6 is shown to be toxic to larvae of three major genera of disease-bearing mosquitos. Factors affecting expression of Bti genes in cyanobacteria are discussed.

Development of a vaccine strategy against human and bovine schistosomiasis: background and update

Schistosomiasis is a chronic and debilitating parasitic disease that affects over 200 million people throughout the world and causes about 500,000 deaths annually. Two specific characteristics of schistosome infection are of primordial importance to the development of a vaccine: schistosomes do not multiply within the tissues of their definitive hosts (unlike protozoan parasites) and a partial non-sterilizing immunity can have a marked effect on the incidence of pathology and on disease transmission. Since viable eggs are the cause of disease pathology, a reduction in worm fecundity whether or not accompanied by a reduction in parasite burden is a sufficient goal for vaccine induced immunity. We originally showed that IgE antibodies played in experimental models a pivotal role for the development of protective immunity. These laboratory findings have been now confirmed in human populations. Following the molecular cloning and expression of a protein 28 kDa protein of Schistosoma mansoni and its identification as a glutathion S-transferase, immunization experiments have been undertaken in several animal species (rats, mice, baboons). Together with a significant reduction in parasite burden, vaccination with Sm28 GST was recently shown to reduce significantly parasite fecundity and egg viability leading to a decrease in liver pathology. Whereas IgE antibodies were shown to be correlated with protection against infection, IgA antibodies have been identified as one of the factors affecting egg laying and viability. In human populations, a close association was found between IgA antibody production to Sm28 GST and the decrease of egg output. The use of appropriate monoclonal antibody probes has allowed the demonstration that the inhibition of parasite fecundity following immunization was related to the inhibition of enzymatic activity of the molecule. Epitope mapping of Sm28 GST has indicated the prominent role of the N and C terminal domains. Immunization with the corresponding synthetic peptides was followed by a decrease of 70% of parasite fecundity and egg viability. As a preliminary step towards phase I human trials, vaccination experiments have been performed in cattle, a natural model for Schistosoma bovis. Vaccination of calves with the S. bovis GST has led to a reduction of ever 80% of egg output and tissue egg count. Significant levels of protection were also observed in goats after immunization with the recombinant S. bovis GST. Increasing evidence of the participation of IgA antibodies in protective immunity has prompted us toward the development of mucosal immunization. Preliminary results indicate that significant levels of protection can be achieved following oral immunization with live attenuated vectors or liposomes. These studies seem to represent a promising approach towards the future development of a vaccine strategy against one of major human parasitic diseases.

The development of species of Leishmania Ross, 1903 in Lutzomyia longipalpis (Lutz & Neiva, 1912)

The development of four isolates of Leishmania from foci of American cutaneous leishmaniasis was studied in Lutzomyia longipalpis. The suggestion that the differences in the development of the Leishmania in the invertebrate host are of great taxonomic significance was confirmed. The pattern of development of three strains was typical of parasites of the subgenus Leishmania, the other was similar to Leishmania of the subgenus Viannia. The identification of the strains using other criteria is in agreement with biological characterization. The results show that the morphological and morphometric study of promastigotes do not clearly define the taxonomic position of the parasites but other studies are needed to confirm this.

Some Aspects of the Development of Lobatostoma jungwirthi Kritscher, 1974 (Aspidogastrea) in Snails and Cichlid Fishes from Buenos Aires, Argentina

The molluscs Heleobia castellanosae and Ampullaria canaliculata and cichlid fishes were collected from an artificial pond at Tres de Febrero Park (Buenos Aires city), between June 1994 and May 1995. One hundred and eighty of 2,467 H. castellanosae examined were infected with pre-adults of Lobatostoma jungwirthi, 112 of them in concurrent infections with digeneans. L. jungwirthi was significantly more prevalent in larger snails, especially those infected with larval digeneans, but the prevalence of infection did not fluctuate significantly throughout the year. A. canaliculata and cichlids smaller than 10 cm were not infected, but larger Cichlasoma facetum harboured adults of L. jungwirthi in their intestines. Experimental infections of C. facetum and Gymnogeophagus meridionalis with pre-adult aspidogastreans obtained from H. castellanosae were successful. The development of L. jungwirthi in the snail host involves five arbitrary growth phases. Its life-cycle is heteroxenous, similar to that described for L. manteri, with H. castellanosae as the intermediate host and cichlid fishes as the definitive host in this pond.

Development of Rhodnius prolixus (Hemiptera: Reduviidae) under Constant and Cyclic Conditions of Temperature and Humidity

Development of Rhodnius prolixus after eclosion until the adult stage was studied at constant temperatures (T), 15, 20, 25, 28, 35°C, and relative humidities (RH), 75, 86 and 97%, and fluctuating (16/8 hr) temperatures, T I/II, 15/28°C, 20/25°C, 25/28°C and 25/35°C, and relative humidities, RH I/II, 86/75% and 97/75%. Eclosion or molting were not observed at 15°C and 86 or 97% RH, respectively. At 35°C and 75% RH only few insects molted. By alternating T I/II, 15/28°C and 25/35°C, insects developed at high frequency. Cumulating the average lengths of the interphases within independent groups for each instar, R. prolixus reached the adult stage most rapidly (86.7 days) and at highest frequency per instar (mean: 91.8%) at 28°C and 75% RH. Under fluctuating T I/II, development was completed within 100 days or less at 25/28°C and 25/35°C with high rates of hatch and molting. Development was slowest at fluctuating TI/II, 15/28°C and 20/25°C (>185 days), and at constant 20°C (>300 days). Mortality was higher at constant 97% RH or fluctuating RH I, 97%, than at constant or fluctuating 86% RH. Refeeding was minimal at optimal conditions of T and RH for development. The most refeeding was observed at a constant 35°C.

Effects of Polydispyrenia simulii (Microspora; Duboscqiidae) on Development of the Gonads of Simulium pertinax (Diptera; Simuliidae)

The effects of the infection caused by the microsporidium Polydispyrenia simulii in gonads of the simuliid Simulium pertinax were evaluated. This blackfly species is the main target of control programmes in southeastern Brazil. Infected and noninfected blackflies were reared from larval stage to adults using a laboratory rearing system. There was no significant difference between the oogenic development and dimensions of ovarian follicles of healthy females compared to those reared from infected larvae. Otherwise, there was a significant difference between the fecundity of healthy females and those reared from infected larvae. In males, there was an evident reduction of motility of spermatozoids of males reared from infected larvae. The results obtained suggest that the microsporidium P. simulii have an important effect on the natural population dynamics of S. pertinax.

The postembryonic development of the ocellar system of Triatoma infestans Klug (Heteroptera: Reduviidae)

Simple eyes or ocelli coexist with compound eyes in many adult insects. The change in the morphology of the ocelli along the five larval instars of Triatoma infestans was studied by light and scanning electron microscopy. Our analysis showed that the development of the ocelli of these bugs occurs gradually along the larval life. The photoreceptor layer is present from the second-instar onwards. The cornea appears first at the imaginal stage and grows up to the 18-20th day after the last ecdysis, associated to an increase in the retinal mass. Findings are discussed in a comparative fashion and in relation to the functionality of the ocellar system in T. infestans.