Experimental heteroxenous cycle of Lagochilascaris minor Leiper, 1909 (Nematoda: Ascarididae) in white mice and in cats

Reports of natural infections of sylvatic carnivores by adult worms of species similar to Lagochilascaris minor in the Neotropical region led to attempts to estabilish experimental cycles in laboratory mice and in cats. Also, larval development was seen in the skeletal muscle of an agouti (Dasyprocta leporina) infected per os with incubated eggs of the parasite obtained from a human case. In cats, adult worms develop and fertile eggs are expelled in the feces: in mice, larval stages of the parasite develop, and are encapsulate in the skeletal muscle, and in the adipose and subcutaneous connective tissue. From our observations, we conclude that the larva infective for the mouse is the early 3rd stage, while for the final host the infective form is the later 3rd stage. A single moult was seen in the mouse, giving rise to a small population of 4th stage larvae, long after the initial infection.

Esparganose em alguns vertebrados do Brasil: dificuldades na identificaçao das espécies de Luheella (Spirometra)

Some species of Amphibia and Reptilia are listed as new hosts of spargana, from material deposited in the Helminthological Collection of Oswaldo Cruz Institute. It is discussed the difficulties in identifying the larvae (Sparganum) and also the identification of adults of Luheella species from South America. The histopathology induced by spargana in the liver of a species of Amphibia is briefly described.

Effector functions of eosinophils in schistosomiasis

The dual function of eosinophils is clearly illustred in schistosomiasis. Well equipped in membrane receptors for immunoglobulins and complement, and due to the presence of granule basic proteins, eosinophils can become cytotoxic for parasite larvae and thus participate to protective immunity. However mediators can also exert their cytolytic effect on normal cells or tissues, inducing therefore pathology. Through ADCC mechanisms against schistosome larvae in vitro involving different antibody isotypes (IgG, IgE and IgA) and also in experiments performed in vivo, eosinophils have been clearly involved in protective immunity. Although no direct evidence of the protective role of eosinophils were brought in humans, the striking association of eosinophil-dependent cytotoxic antibody isotypes with resistance to reinfection (for instance IgE and IgA antibodies), whereas in vitro blocking antibody isotypes (IgG4, IgM) were detected in susceptible subjects, strongly, suggested the participation of eosinophils in antibody-dependent protective immune response. However eosinophils could also participate to granuloma formation around S. mansoni eggs and consequently to the pathological reactions induced by schistosomiasis.

Capillaria hepatica: a cause of septal fibrosis of the liver

Fine, long, fibrous septa were observed as a late change developing in the acinar zone III of the liver of rats experimentally infected with the helminth Capillaria hepatica. Hepatic septal fibrosis begun 30 days after inoculation of embryonated eggs into the stomach of rats and became clearly evident from the 40th day onwards. Experimental observation was undertaken for 170 days. Septal fibrosis increased progressively with time and was most marked when the parasitic nodules formed around larvae, disintegrating worms and eggs were involving. Septal fibrosis of the liver has not been previously recognized as a manifestation of hepatic capillariasis. The presence of sequestered parasite antigens, probably being slowly released within the liver, appears to be a major factor in the pathogenesis of hepatic septal fibrosis observed in rats with C. hepatica infection.

Biochemistry and mode of action of the Bacillus sphaericus toxins

Bacillus sphaericus produces at least two toxins which are highly toxic to mosquito larvae. The binary toxin, which is comprised of proteins of 51.4 and 41.9 kDa, is present in all highly insecticidal strains. The 100 kDa SSII-1 toxin is present in most highly insecticidal as well as the weakly insecticidal strains. The current status of studies on biochemistry and mode of action of these toxins is reviewed.

Bacillus and Serratia species for Scarab control

Few microorganisms are commercially available for use against white grubs (larvae of Scarabaeidae). Entomopathogenic bacteria, particularly Bacillus popilliae, have been used the longest for white grub suppression. Other bacteria, namely B. thuringiensis and Serratia spp. offer promise for future control. This papes examines two genera of bacteria (Bacillus and Serratia) from the historical and current perspective. Bacillus popilliae, the firs microbial control agent registered in the United States, has a long history of use in suppressing populations of the Japanese beetle, Popillia japonica. However, lack of in vitro production and the slow and sporadic nature of its activity, severely limits its utilization. B. thuringiensis, the most widely used microbial pesticide, has not been used for scarab, control. However, strains with scarab activity have recently been discovered. Scarab larvae have been collected in the United States with signs and symptoms similar to those characteristic of amber disease (caused by Serratia entomophila) in the New Zealand grass grub, Costelytra zealandica. A total of 147 bacteria have been obtained from the digestive tracts of larvae of the Japanese beetle and masked chafers, Cyclocephala spp., as well as from larvae and soil collected in Japan and China. Seventy five of these have been identified as Serratia spp. Most (40) of the remaining bacteria are in the genus Enterobacter. A majority of the bacteria (73) and of the Serratia (38) came from P. japonica.

Transfer of toxin genes to alternate bacterial hosts for mosquito control

Mosquitoes are vector of serious human and animal diseases, such as malaria, dengue, yellow fever, among others. The use of biological control agents has provide an environmentally safe and highly specific alternative to the use of chemical insecticides in the control of vector borne diseases. Bacillus thuringiensis and B. sphaericus produce toxic proteins to mosquito larvae. Great progress has been made on the biochemical and molecular characterization of such proteins and the genes encoding them. Nevertheless, the low residuality of these biological insecticides is one of the major drawbacks. This article present some interesting aspects of the mosquito larvae feeding habits and review the attempts that have been made to genetically engineer microorganisms that while are used by mosquito larvae as a food source should express the Bacillus toxin genes in order to improve the residuality and stability in the mosquito breeding ponds.

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.

Bacillus sphaericus mosquito pathogens in the aquatic environment

The fate of Bacillus sphaericus spores in the aquatic environment was investigated by suspending spores in dialysis bags in fresh and seawater. Spore viability was lost more rapidly in seawater. Neither B. sphaericus nor B. thuringiensis israelensis (B.t.i.) spores mixed with pond sediment appeared to attach to the sediment. However, rapid decrease in B.t.i. toxicity suggested attachment of parasporal bodies to sediment. B. sphaericus toxin settled more slowly and less completely. B. sphaericus spores fed to larvae of four aquatic invertebrates were mostly eliminated from the animal gut in less than one week. An exception was the cranefly (Tipula abdominalis) where spores persisted in the posterior gut for up to five weeks.

Wyeomyia luteoventralis Theobald, the type species of the subgenus Dendromyia Theobald (Diptera: Culicidae)

Wyeomyia (Dendromyia) luteoventralis is redescribed from females, males, larvae and pupae collected at the type locality, in Brazil, and compared to the closely related species. At least six species - Wy. luteoventralis, Wy. ypsipola, Wy. testei, Wy. trifurcata, Wy. complosa and Wy. jocosa - appparently, belong to a monophyletic group, the subgenus Dendromyia. All other species previously included in Dendromyia are hereby excluded from this subgenus and retained in genus Wyeomyia without subgeneric placement.

Effects of three organophosphorus insecticides in the reproductive potential of Culex quinquefasciatus

A Culex quinquefasciatus Say 1823 strain with resistant genes to organophosphates was tested in the laboratory to know the reproductive potential after exposure, as larvae, at the LC30 and LC70 (mg/l) of three organophosphorus insecticides: malathion, chlorpyrifos and methyl-pirimiphos. Data showed that fecundity was decreased significantly by malathion at LC30 = 0.0025 and LC70 = 0.0075, whereas fertility has a no significant decrement by chlorpyrifos and methyl-pirimiphos at the LC70 (0.000016, 0.00043). The sexual index was affected by chlorpyrifos and methyl-pirimiphos showing a greater number of adult females.

The biology of Aedes (Ochlerotatus) albifasciatus Macquart, 1838 (Diptera: Culicidae) in Central Argentina

Aedes albifasciatus is a flood water mosquito ocurring in the southern countries of South America. It is a competent vector of the Western Equine Encephalitis (WEE) and causes important losses on milk and beef production in central Argentina. Field work was carried out from December 1990 to March 1993, on a monthly basis during the dry season and biweekly during the rainy season. Larvae were collected using the 'dipping' technique and females with CDC traps baited with CO2. Field collected larvae were used to build laboratory cohorts, from which basic population parameters were estimated. Eggs survived up to six months on dry soil, although there was a linear decrease of viability with time. At 23ºC, larval development time was around nine days, and all adults emerged within one week. The estimation of larval development in the laboratory seems to be very near the development on the field, as larvae have been collected on average eight days after a rainfall. Egg to adult survival was 83%, with the highest mortality on fourth larval instar (6%). In the laboratory studies, sex proportion among the adults was 1:1, females lived longer than males (median 13 and five days, respectively), and adult survival pattern showed a constant number of individuals dying per unit time. Field collected females layed an average of 84 eggs per batch, and completing up to five gonotrophic cycles, suggesting an estimated survival of up to 35-50 days.

Larval and pupal periods of Peckia chrysostoma and Adiscochaeta ingens (Diptera: Sarcophagidae) reared under laboratory conditions

Peckia chrysostoma obtained mean viability of 97.0±2.4% for larvae and of 96.9±2.5% for pupae (total viability of 94.0±3.7%). Adiscochaeta ingens obtained mean viability of 93.0±7.5% for larvae and of 92.8±7.6% for pupae (total viability of 86.0±7.3%). P. chrysostoma obtained mean larval period of 185±4 hr at 18ºC, of 94±2 hr at 27ºC and of 88±2 hr at room temperature (range of 23ºC and 29ºC). A. ingens obtained mean larval period of 169±1 hr at 18ºC, of 77±1 hr at 27ºC and of 84±2hr at room temperature. P. chrysostoma obtained mean pupal period of 23.5±1.3 days at 18ºC, of 12.5±0.7 days at 27ºC and of 15.5±0.7 days at room temperature. A. ingens obtained mean pupal period of 33.0±2.2 days at 18ºC, of 16.0±1.0 days at 27ºC and of 19.0±1.0 days at room temperature.

The immature stages of Myiotabanus barrettoi fairchild (Tabanidae-Diptera-Insecta)

Larva and pupa of Myiotabanus barrettoi living between leaves of Pistia stratiotes in ponds of Formosa Province (Argentina) are described. As immature stages of Lepiselaga crassipes inhabit the same environment and have very a similar appearance, new information on ornamentation and morphology is added to differentiate both species. Larvae and pupae were maintained individually in moist vials at laboratory temperature until adults emerged.

Biochemical, immunological and toxicological characteristics of the crystal proteins of Bacillus thuringiensis subsp. medellin

Characterization of the insecticidal and hemolytic activity of solubilized crystal proteins of Bacillus thuringiensis (Bt) subsp. medellin (Btmed) was performed and compared to solubilized crystal proteins of isolates 1884 of B. thuringiensis subsp. israelensis (Bti) and isolate PG-14 of B. thuringiensis subsp. morrisoni (Btm). In general, at acid pH values solubilization of the Bt crystalline parasporal inclusions (CPI) was lower than at alkaline pH. The larvicidal activity demonstrated by the CPI of Btmed indicated that optimal solubilization of CPI takes place at a pH value of 11.3, in Bti at pH values from 5.03 to 11.3 and in Btm at pH values from 9.05 to 11.3. Hemolytic activity against sheep red blood cells was mainly found following extraction at pH 11.3 in all Bt strains tested. Polyacrylamide gel electrophoresis under denaturing conditions revealed that optimal solubilization of the CPI in all Bt strains takes place at the alkaline pH values from 9.05 to 11.3. An enriched preparation of Btmed crystals was obtained, solubilized and crystal proteins were separated on a size exclusion column (Sephacryl S-200). Three main protein peaks were observed on the chromatogram. The first peak had two main proteins that migrate between 90 to 100 kDa. These proteins are apparently not common to other Bt strains isolated to date. The second and third peaks obtained from the size exclusion column yielded polypeptides of 68 and 28-30 kDa, respectively. Each peak independently, showed toxicity against 1st instar Culex quinquefasciatus larvae. Interestingly, combinations of the fractions corresponding to the 68 and 30 kDa protein showed an increased toxicity. These results suggest that the 94 kDa protein is an important component of the Btmed toxins with the highest potency to kill mosquito larvae. When crystal proteins of Bti were probed with antisera raised independently against the three main protein fractions of Btmed, the only crystal protein that showed cross reaction was the 28 kDa protein. These data suggest that Btmed could be an alternative bacterium for mosquito control programs in case mosquito larval resistance emerges to Bti toxic proteins.