Autosomal recessive hydrocephalus due to aqueduct stenosis: report of a further family and implications for genetic counselling.

We report on two abortuses with hydrocephalus due to congenital stenosis of the aqueduct of Silvius. The occurrence of this disorder in two siblings (a male and a female) with normal parents supports the autosomal recessive pattern of inheritance. Such a mechanism of inheritance should be taken into account when counselling families with congenital hydrocephaly due to aqueduct stenosis.

[Susceptibility of Aedes aegypti larvae to parasitism by Romanomermis culicivorax in laboratory and field conditions in Oaxaca, Mexico]. / Susceptibilidad de las larvas de Aedes aegypti al parasitismo por Romanomermis culicivorax en condiciones de laboratorio y de campo en Oaxaca, México.

In June 1996 in the state of Oaxaca, Mexico, larvae of the mosquito species Aedes aegypti were exposed to infective preparasites of the nematode Romanomermis culicivorax, Ross and Smith, in the laboratory and in the field. For the laboratory experiments larvae in instars I-IV were used; they had been collected in natural reservoirs. The laboratory experiments were carried out in triplicate, with 100 larvae of each larval stage per experiment. Three preparasite application dosage ratios were tested: 5, 10, or 15 preparasites per mosquito larva. For the field studies 13 A. aegypti outdoor breeding sites were used, with larvae in instars I-IV and a 15:1 preparasite dosage ratio. With the laboratory experiments, an increase was observed in the average infestation of the larvae as the preparasite application ratio was increased from 5:1 to 15:1. With a 10:1 ratio, the rates of parasitism were 100%, 100%, 85%, and 74% in the larvae in instars I, II, III, and IV, respectively; for the 15:1 preparasite ratio, parasitism rates were 100%, 100%, 90%, and 79%, respectively. The field tests with the 15:1 preparasite dosage ratio in the 13 outdoor reservoirs produced parasitism rates of 80% to 98%, thus demonstrating the susceptibility of this species of mosquito to parasitism by R. culicivorax in Oaxaca, Mexico.

The Romanomermis iyengari parasite for Anopheles pseudopunctipennis suppression in natural habitats in Oaxaca State, Mexico.

In September and November 1996 Romanomermis iyengari Welch, a parasite of larval mosquitoes, was released in 44 natural larval habitat sites of Anopheles pseudopunctipennis Theobald in an attempt to reduce the larval populations of this important malaria vector. The selected treatment sites ranged in size from 5 to 500 m2. The study was carried out in Pochutla District of Oaxaca State, on the Pacific coast of Mexico. Chemical pesticides to reduce vector populations have been the principal tool in malaria suppression campaigns. However, the excessive use of these chemicals has created pesticide resistance and other serious collateral problems. Therefore, a biological control project using agents that are pathogens of Anopheles larvae was initiated in 1996. The principal objective was to establish mass rearing capacities for R. iyengari. Detailed methodology for rearing and introducing these nematodes into mosquito larval habitats was established at the National Polytechnic Institute of Oaxaca State. Before application of the parasites to larval habitats, site characteristics were determined, including size, depth, aquatic vegetation, salinity, pH, conductivity, temperature, and pretreatment larval density. With a compressed air sprayer, infective mermithid parasites were released at rates of either 2,000 or 3,000/m2, and the parasites produced high levels of infection. Anopheles populations were sampled 72 h posttreatment, and the larvae obtained were taken to the laboratory and examined through microscopic dissection to determine infection levels and mean parasitism. Nematode parasitism ranged from 85 to 100% at all the treatment sites, even though no previous information concerning field parasitism of An. pseudopunctipennis by R. iyengari has been reported. In addition, a significant reduction of mosquito larval density at the treatment sites was found five days after the nematode application. Levels of parasitism were indicative of the number of mosquito larvae killed by the treatment since infected larvae never progressed to the pupal stage. Results from sampling nine of the sites 2 months after the initial application of nematodes indicated that a high number of mosquito larvae were infected by parasites that had emerged from eggs previously deposited in the stratum. This work suggests the potential of this mermithid to reduce An. pseudopunctipennis populations in Oaxaca State.

[The susceptibility of Anopheles pseudopunctipennis larvae to parasitism by the nematode Romanomermis iyengari (Nematoda: Mermithidae), the state of Oaxaca, Mexico]. / Susceptibilidad de las larvas de Anopheles pseudopunctipennis al parasitismo del nematodo Romanomermis iyengari (Nematoda: Mermithidae), Estado de Oaxaca, México.

Mosquito larvae of the species Anopheles pseudopunctipennis Theobald 1901 were studied under laboratory and field conditions to evaluate the level of susceptibility to the parasitism of nematode Romanomermis iyengari Welch 1964. Doses of 5:1 and 10:1 and development stage II larvae collected in natural reservoirs were used for the laboratory assays. A dose of 1,000 preparasitic agents/m2 was applied to field trials. The results of the lab and field tests yielded high levels of infestation in larvae with values ranging from 90 to 100% and from 85 to 95%, respectively. A marked reduction of the larval densities was observed in the 5 treated reservoirs seven days later, which showed an elevated susceptibility of the anopheline species to mermithid parasitism.

Reduction of mosquito larval densities in natural sites after introduction of Romanomermis culicivorax (Nematoda:Mermithidae) in Cuba.

Romanomermis culicivorax Ross & Smith became established in 4 of 6 treated sites and produced high levels of infection in Anopheles albimanus Wiedemann, Culex atratus Theobald, Psorophora confinnis Lynch-Arribálzaga, and Uranotaenia sapphirina Oster-Sacken mosquitoes for 9 wk in 1993. Mean levels of southern house mosquito parasitism ranged from 82 to 83% for Culex quinquefasciatus Say, at 2 sites, from 89 to 95% for An. albimanus at 4 sites, and from 78 to 80% at 2 sites for Cx. atratus, Ps. confinnis, and Un. sapphirina. Results indicated that R. culicivorax has potential use as biological control agent against mosquitoes in several different habitats in Cuba.