On the developmental velocity of Wucheria bancrofti larvae in vector mosquitoes of different susceptibility to filarial infections.

The developmental velocity of Wucheria bancrofti larvae was investigated in mosquito strains with different susceptibility to this filarial species. High susceptibility of the vector strains favoured fast filarial development, e.g. between 17.1 and 25.9% of all discovered larvae on day 13 p.i. had already migrated to the head and mouth parts of the more and partly even highly susceptible Anopheles gambiae, Culex pipiens quinquefasciatus and Aedes aegypti, respectively, whereas between 0 and 3.4% infective larvae had reached the head in the less susceptible Culex strains. On day 15 p.i. in all mosquito strains the majority of the larvae had reached infectivity.

On the uptake of Wuchereria bancrofti microfilariae in vector mosquitoes of different susceptibility to filarial infections.

The quantitative uptake of Wuchereria bancrofti microfilariae by mosquito species of different susceptibility to filarial infection was studied. There was no relationship between the degree of susceptibility and the number of ingested microfilariae. However, in all tested mosquito strains the females ingested as a mean 1.2-1.9 times more microfilariae of W. bancrofti than expected.

On the infectivity of early third-stage Brugia larvae isolated from the abdomen of Aedes aegypti.

Third-stage larvae (L3) of Wuchereria bancrofti, Brugia malayi and B. pahangi are known to be recovered not only from the head and thorax but also from the abdomen of dissected vector mosquitoes. For epidemiological reasons, was of interest to determine whether L3 larvae from the abdomen of the vector would be infectious for the final host. Early abdominal L3 larvae of B. pahangi isolated as early as on day 7 post-infection (p.i.) from Aedes aegypti were injected s.c. into five male Meriones unguiculatus. Four of the five jirds were microfilaria-positive after 67 days.

[Tolerance of Haemofusin in hemodilution and volume substitution]. / Untersuchungen zur Verträglichkeit von Haemofusin in der Hämodilution und Volumensubstitution.

In an open and uncontrolled trial the frequency and the type of adverse events were registered in patients who received Haemofusin, a hydroxyethyl starch solution, either for volume substitution or haemodilution. A total of 379 patients were investigated. No serious allergic reaction occurred. Headache, fever, rigor, light allergic reactions and nausea were documented in 17 patients. Even if one assumes that these observed concomitant events were caused by the hydroxyethyl starch, Haemofusin proved to be a well-tolerated colloid with a low rate of side effects (4.5%).

The susceptibility of Liberian Culex quinquefasciatus to Wuchereria bancrofti in Sri Lanka.

Strains of Culex quinquefasciatus collected in Liberia showed low susceptibility to Wuchereria bancrofti from Liberian donors. However, when the same mosquito strains were fed on W. bancrofti donors from Sri Lanka they showed equally high susceptibility as Sri Lankan C. quinquefasciatus simultaneously fed on the same donors. A Liberian strain did not respond to selection for refractoriness. Thus the strains of W. bancrofti from Liberia and Sri Lanka differ in their ability to infect specific mosquito strains and it is concluded that Liberian C. quinquefasciatus could not provide genes for use in the construction of a refractory strain intended for the replacement of Sri Lankan vector populations.

Studies on bancroftian filariasis in Liberia, West Africa. V. The influence of treatment with diethylcarbamazine and vector control on the transmission of Wuchereria bancrofti.

The transmission intensity of bancroftian filariasis was investigated during a study on filariasis control carried out in eight villages of the savanna area in the hinterland of Liberia. Although the microfilarial reservoir had been reduced considerably in the human population of two villages by mass treatment with the filaricide drug diethylcarbamazine the transmission of Wuchereria bancrofti was continued without any distinct reduction. The transmission however decreased distinctly or was even interrupted when residual spraying with DDT was used in two other villages for vector control. The combined application of both control measures did not prevent completely that mosquitoes became infected with mature stages of W. bancrofti.

Studies on Bancroftian filariasis in Liberia, West Africa. IV. Notes on side effects observed during a diethylcarbamazine treatment campaign in a rural area endemic for Wuchereria bancrofti and Onchocerca volvulus.

464 persons of whom 189 proved to be infected with microfilariae of Wuchereria bancrofti and/or Onchocerca volvulus were examined for adverse reactions due to diethylcarbamazine, which was administered during a filariasis control campaign. Persons older than 20 years of age were significantly more affected than younger persons and men showed distinctly more side effects than women. The most frequent complaints were skin reactions followed by gastrointestinal complications. The significantly highest rate of adverse reactions was observed in persons being infected with microfilariae of O. volvulus, whereas no significant difference was registered between side effect rates of bancroftian microfilaria carriers and non-infected persons. It is concluded that in areas where both filarial species are endemic, infections with O. volvulus are a limiting factor for the control of bancroftian filariasis by means of mass treatment with diethylcarbamazine.

Scanning electron microscope study on larvae of Wuchereria bancrofti from the vector and from experimental rodent hosts.

The surface structures of larvae of Wuchereria bancrofti from Liberia were examined by scanning electron microscopy. For this study microfilariae from man, first-stage, second-stage, and third-stage larvae from the vector Aedes aegypti, and fourth-stage larvae from the experimental rodent hosts Mastomys natalensis and Meriones unguiculatus were available. From these larvae the structure of the anterior ends, the cuticle in the midbody regions, and the posterior ends are presented. As an obvious structure at the anterior end of the microfilaria and the first-stage larva there is a cephalic cap with a hook on its left side. Three spines are found on the right side close behind the border of the cap. The amphidial openings are found immediately beside the cephalic cap. A simply formed oval mouth is found in the second-stage larva. A small elevation is situated on each side of the mouth. On the anterior end of the third-stage larva there are eight papillae. The four outer papillae are round, the four inner papillae are cone-shaped. The caudal extremity of this larva carries three characteristic bubble like papillae. The mouth of the fourth-stage larva from the experimental rodent host is surrounded by an oral field. The cephalic papillae are indented and the amphidial openings are associated with papillary protuberances. The cuticle of these larvae is regularly annulated. On the caudal extremity, the dorsal papilla is reduced.

Studies on Bancroftian filariasis in Liberia, West Africa. III. Efficacy of repeated treatment with diethylcarbamazine and vector control on the microfilarial reservoir in a rural population.

The population of four villages in the savanna area in Upper Lofa in the hinterland of Liberia was treated with diethylcarbamazine and the decline of the density of microfilariae of Wuchereria bancrofti was studied. It became obvious that even a repeated treatment with the drug did not result in a complete eradication of the parasites, but that about one third of microfilaria carriers who had received two courses of treatment remained infected, showing ultra low densities which could only be-discovered by employing the sensitive membrane filtration technique. Vector control by means of residual spraying with DDT carried out every six months for 2 1/2 years in two villages did not result in a decrease of the microfilaria carrier rates. However, the microfilarial density of the infected persons declined distinctly during the three years of control. Experiences made with the membrane filtration technique under field conditions are described.

On the longevity and behaviour of microfilariae of Wuchereria bancrofti, Brugia pahangi and Dirofilaria immitis transfused to laboratory rodents.

Microfilariae of Wuchereria bancrofti and Brugia pahangi, which were inoculated into Meriones unguiculatus and Mastomys natalensis respectively, were found in the peripheral blood of the rodents until the ninth day after infection, but no microfilarial periodicity was observed. Microfilariae of W. bancrofti disappeared much faster from the peripheral blood of jirds after reinfection than after the first inoculation. Microfilariae of Dirofilaria immitis inoculated into M. natalensis and laboratory mice were recovered in the peripheral blood until the 17th day after infection and remained infective to mosquitoes. For the first few days the microfilarial periodicity observed in the rodents was similar to that observed in the donor dog, but then reversed.

Attempts to infect Meriones unguiculatus and Mastomys natalensis with Wuchereria bancrofti from West Africa.

44 male and female Meriones unguiculatus and 13 male Mastomys natalensis were inoculated with infective stage larvae of Wuchereria bancrofti from West Africa and dissected between 16 and 360 days after inoculation. Fourth stage larvae of W. bancrofti were recovered in Meriones until the 90th day p.i. and in Mastomys until the 175th day p.i. The longest larva obtained from Meriones measured 9.5 mm and from Mastomys 6.5 mm.

Quantitative aspects of the development of mosquito transmitted Brugia malayi and Brugia pahangi and their distribution in Jirds, Meriones unguiculatus.

Twenty-two jirds, Meriones unguiculatus, were exposed to the bites of 2250 females of Aedes aegypti carrying an estimated total of 2464 larvae of Brugia malayi, and 13 jirds were offered for blood feeding to 1450 mosquitoes infected with about 4460 larvae of Brugia pahangi. On necropsy of the jirds, four months after feeding of the mosquitoes, a total of 88 adult filariae of B. malayi and 143 of B. pahangi were recovered in 20 and 13 jirds respectively. The majority of the adult filariae was obtained from the testes (48,9% of B. malayi and 53,2% of B. pahangi), from the heart-lung-system (26,1% and 45,6%), and additional in B. malayi from the tail (19,3%). It can be estimated that 3,6% (3,2%) of all infective larvae of B. malayi (B. pahangi), carried by Aedes aegypti females before feeding, reached maturity in the jird host after they had left the vectors during the blood meal. Microfilariae were found in the peripheral blood in seven of B. malayi infected jirds and in eleven of the jirds infected with B. pahangi.

Studies on bancroftian filariasis in Liberia, West Africa. II. Changes in microfilaraemia in a rural population some years after first examination.

The population of eleven villages in the savanna area in Upper Lofa in the hinterland of Liberia was investigated in 1973 and 1976/77 for infections with microfilariae of Wucheria bancrofti. From a total of 1255 persons examined in 1973 16,3% were microfilaria carriers and in 1976/77 17,9% out of 1356 inhabitants were microfilaria positive. To obtain informations on the change of microfilaraemia in individuals, emphasis was laid in 1976/77 on the identification of those persons, who had been examined already in 1973. From 477 persons examined in both surveys 78 proved to be infected with microfilariae and 348 were microfilaria negative in both examinations. 35 inhabitants were microfilaria positive only in 1976/77 and 18 persons showed microfilariae in the blood samples only in 1973. The median density of microfilariae of the microfilaria carriers examined in 1973 and 1976/77 increased little but statistically significantly within a period of about three years.

Notes on nematode larvae others than microfilariae found on filter membranes in blood surveys for bancroftian filariasis.

Among 741 people examined in a rural area in Liberia for microfilariae of Wuchereria bancrofti 39 (5,3%) were found to be infected with nematode larvae others than microfilariae. These larvae had more developed inner structures than microfilariae and could be classified into two different types, differing in length and shape. The larvae have not been identified yet, but it is believed that they have to be associated to parasitic nematodes of the intestine.

Studies on Bancroftian filariasis in Liberia, West Africa. I. Distribution and prevalence in the north-western savanna area.

A nightblood survey was carried out in 17 villages in the savanna area in Upper Lofa in Liberia. A total of 1968 people was examined for the prevalence of microfilariae of Wuchereia bancrofti and for clinical symptoms of filariasis. 279 (14,2%) persons proved to be microfilaria carriers. Men were almost twice (19,0%) as much infected than women (10,4%). Only two cases of leg elephantiasis and one breast elephantiasis were found. Enlargements of scrotum were seen in 60 men (6,9%). The scrotal enlargement rate increased steadily with age.

Abortive development of Wuchereria bancrofti in a West African strain of Culex pipiens fatigans.

The detailed morphology of the larvae of Wuchereria bancrofti developing in a refractory strain of Culex pipiens fatigans from Liberia, West Africa, has been described. The abortive development of the parasite in the thoracic muscles of the mosquito was characterized mainly by: (i) retardation or complete failure of initial division of the G-cell, (ii) partial or complete encapsulation of developing larvae, especially at the anal and excretory vesicle areas of late first-stage, (iii) breakdown of the forming internal structures with formation of clusters of DNA-and RNA-positive material, and (iv) anomalous development of some larvae in which extra-corporeal growth of internal tissues took place.