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PubMed1994

[The hosts of Glossina fuscipes fuscipes Newstead, 1910 (Diptera: Glossinidae) in 2 animal breeding zones in the Central African Republic].

From 1987 to 1993, a survey on the feeding behavior of Glossina fuscipes fuscipes was conducted in the Central African Republic. A total of 556 blood-meal samples was analyzed by ELISA. According to the results, the number of blood meals from cattle was rather low (12% on average). During the rainy season, this number increased significantly and varied according to the sampling area. Along the riverine forests, this amounted to 5%, while blood meals from wild ruminants amounted to 87%. In the neighborhood of watering-places, the number of cattle blood meals reached 9-22%. Reptiles were found to be important hosts (17-35%). In all cases, man presented a non-negligible host (4-14%), similar to suidae (2-19%). The authors discuss the relevance of these results to risk of trypanosomes transmission.

Animals↗
PubMed1993

The ecology and behaviour of the forest form of Anopheles gambiae s.s.

Studies on the ecology of Anopheles gambiae s.s. and the transmission of malaria were undertaken in a high rainfall forested area in southern Sierra Leone. Anopheles gambiae s.s., identified by chromosomal techniques as the Forest form, was the only malaria vector in the study village. Surprisingly, rice fields or swamps were not favoured breeding places for this species; breeding mainly occurred in temporary pools. The mean annual sporozoite rate of An. gambiae s.s. determined by ELISA was 3.9%. Pyrethrum spray, human bait, and exit trap collections, as well as identification of mosquito blood-meals using the ELISA method, showed that the forest chromosomal form of An. gambiae s.s. was highly anthropophagic and exophilic.

Animals↗
PubMed1993

Mosquito repellent action of neem (Azadirachta indica) oil.

Two percent neem oil mixed in coconut oil, when applied to the exposed body parts of human volunteers, provided complete protection for 12 h from the bites of all anopheline species. Application of neem oil is safe and can be used for protection from malaria in endemic countries.

Animals↗
PubMed1993

Neem oil as a sand fly (Diptera: Psychodidae) repellent.

The repellent action of neem oil was evaluated against sand flies under laboratory and field conditions. Concentrations of 2% neem oil mixed in coconut or mustard oil provided 100% protection against Phlebotomus argentipes throughout the night under field conditions; against Phlebotomus papatasi it repelled sand flies for about 7 h in the laboratory. Neem oil is an indigenous product and a low-cost alternative for personal protection against sand fly bites.

Animals↗
PubMed1993

Man-fly contact in the Gambian trypanosomiasis focus of Nola-Bilolo (Central African Republic).

A study using bipyramid tetse fly traps in the Nola-Bilolo sleeping sickness focus (Central African Republic) reveals ecological and behavioural differences between two vectors, Glossina palpalis palpalis and G. fuscipes fuscipes. The latter species inhabits mainly open water sites and surrounding forest, whereas G. p. palpalis occurs mainly in coffe plantations near villages. Consequently, the man-fly contact differs considerably according to the species. The intensity of trypanosomiasis transmission, estimated by the probable distribution of cases, showed significant positive correlation with the density of the flies. Analysis of the fly blood meals in two villages show that, unlike G. g. palpalis, G. f. fuscipes feeds on men more than on pigs. Trypanosoma vivax infection was observed only in G. fuscipes fuscipes. The differences in occupation of the environment between the two vectors must be taken in account in trapping programmes which may modify this distribution.

Animals↗
PubMed1993

Ecology of mosquitos (Diptera: Culicidae) at a site endemic with Japanese encephalitis on Luzon, Republic of the Philippines.

A 2-year study of the ecology of mosquitos was conducted in a rice-growing area in the Philippines. Forty-four species in 8 genera were collected using 6 techniques, with Culex vishnui being most abundant. Of all the Anopheles collected, most species were exophagic, while most of the Culex species collected were endophagic. Anthropophilic or zoophilic feeding patterns were estimated using man-to-animal biting ratios. Peak periods of mosquito abundance occurred several months after the onset of both the rainy season and the rice irrigation period. Seasonal populations of the more abundant species revealed 3 distinct patterns: 1) populations are high during the rainy season and low during the irrigation period; 2) populations are equally strong during both periods; and 3) populations are highest during the irrigation period. Species' biting activity was grouped into 2 patterns: 1) those that feed primarily from 1800-0000; and 2) those that feed evenly throughout the night. Mosquito abundance and Japanese encephalitis virus activity were related to rainfall and rice-growing practices.

Animals↗
PubMed1993

Parasites and the behavior of biting flies.

Biting fly behavior involved in parasite transmission is reviewed. Except for the areas of activity and probing, few investigations have addressed ways in which parasites might alter vector behavior. Given the manner in which parasites alter behavior in other arthropods (e.g., habitat choice, color preference), it is reasonable to expect infected hematophagous flies to behave differently from uninfected conspecifics. This could have important epidemiological consequences.

Animals↗
PubMed1995

Vectorial capacity and entomological inoculation rates of Anopheles gambiae in a high rainfall forested area of southern Sierra Leone.

We report the first study of gonotrophic cycle duration, survival rates, pre-gravid rates, vectorial capacity and chromosomal polymorphism of Anopheles gambiae s.s. in Sierra Leone. In the village of Bayama in the Southern Province, An. gambiae was the only species found to be naturally infected with Plasmodium falciparum and it constituted 99.7% of 22,541 anopheline mosquitoes caught. Chromosomal studies revealed only An. gambiae s.s. out of 66 females examined for chromosomal polymorphism, 61 (92.4%) had the 2LA inversion in the standard arrangement. Other inversions observed in low frequencies included 2Rcu and 2Ru. We estimated a gonotrophic cycle length of three days and survival rate per gonotrophic cycle of 0.59 for this species. The mean daily survival rate of An. gambiae was 0.85 and the entomological inoculation rate was 1,235 infective bites/person/year. Blood-meal ELISA tests showed that the species was very anthropophagic and that there were an estimated 35.4 daily inoculations per infective case. The epidemiological significance of these entomological parameters is discussed in the light of parasitological results for nearby villages.

Animals↗
PubMed1995

Biting activity of the malaria vector, Anopheles culicifacies, on man and cattle in Doon valley, India.

In the present study, the information about biting time and activity of a malaria vector, Anopheles culicifacies on man and cattle in Doon valley has been mentioned. The maximum biting activity, 22.4 percent in human bait indoor and 20.5 percent in human bait outdoor was noted between 22.00-23.00 h in the night. However, the biting activity on animal bait (calf) was noted maximum in the mid night at 24.00-01.00 h.

Animals↗
PubMed1995

[The role of the Aedes aegypti vector in the epidemiology of dengue in Mexico].

The role of Aedes aegypti (Lineo) in the epidemiology of dengue fever in Mexico is herein discussed based on the vectorial capacity model. Comments on the advantages and disadvantages of each model component at the time of field determinations are also presented. Emphasis is made on the impact of sampling and method bias on the results of vectorial capacity studies. The paper also addresses the need to increase vector biology knowledge as an input for epidemiological work to explain and predict dengue fever outbreaks. Comments on potential entomological variables not considered by the quantitative model are included. Finally, we elaborate on the introduction of Aedes albopictus (Skuse) in Mexico as a new risk factor and on its implications for the understanding of dengue fever transmission in Mexico.

Aedes↗
PubMed1996

Sporozoite transmission of three strains of Plasmodium knowlesi to Aotus and Saimiri monkeys.

Attempts were made to infect Aotus and Saimiri monkeys with sporozoites of 3 strains of Plasmodium knowlesi to determine the potential of these animals in a monkey/malaria model. Splenectomized Saimiri and Aotus monkeys were infected with the H strain of P. knowlesi via sporozoites from Anopheles dirus mosquitoes. Prepatent periods ranged from 5 to 16 days. Saimiri monkeys infected with the Philippine strain had prepatent periods ranging from 6 to 8 days. Saimiri monkeys infected with the Hackeri strain had prepatent periods ranging from 6 to 11 days. Exoerythrocytic (EE) stages of the Philippine strain were readily demonstrated; EE stages of the H strain were less abundant. Results indicate that the Philippine strain of P. knowlesi in Saimiri monkeys has a course of parasitemia and EE stages similar to those previously seen in macaques and could serve as a reproducible model for biologic and immunologic studies.

Animals↗
PubMed1995

An animal study on transmission of hepatitis B virus through mosquitoes.

Three gena of mosquitoes were fed with human blood infected with hepatitis B virus (HBV) artificially. When blood in the stomach was completely digested, mosquitoes were used to bite monkeys Tupaia Belangeri. A month after biting, venous blood samples were taken from the monkeys to detect serum HBsAg, HBeAg, Anti-HBs and Anti-HBc. Among 29 test monkeys, 9 were HBV infective serum markers positive. In 4 of 16 test monkey liver biopsies, acute inflammatory changes were found with Hematoxylin-Eosine staining. In the hepatic cells, HBsAg and HBcAg were detected by immunohistochemical double-labeling assays, and HBV-DNA was also positive by in situ hybridization in monkey liver sections. These results provided an evidence for the possibility of transmission of HBV through mosquitoes and suggest its epidemiological significance in mosquito infested areas.

Animals↗
PubMed1996

Experimental and field studies on some biological characteristics of Plasmodium vivax isolated from tropical and temperate zones of China.

OBJECTIVE: To clarify some biological behaviors of Plasmodium vivax including the periodical infectivity of gametocytes for mosquitoes, the prepatent period, the incubation period, the relapse patterns and their relationship. METHODS: Laboratory reared Anopheles sinensis were fed through fetal membrane on blood from patients naturally infected with vivax malaria. After feeding at different hours, the engorged mosquitoes kept in the insectarium were dissected 5-7 days later. The percentage of mosquitoes infected and the mean number of oocysts per gut were taken as criteria of the viability of the gametocytes. The healthy volunteers artificially infected by mosquito bite or quantitative inoculation of sporozoites were treated with 1.5 g chloroquine base alone before and after the first and subsequent onset of fever to detect the natural course of disease in human body. RESULTS: The infection in mosquitoes can readily be divided into upward, peak, downward and non-infective period. The infectivity reached a peak at interschizogony period and fell to low level at the time when schizogony occurred. The short incubation period was frequently observed in persons bitten by 10 infected mosquitoes or 10 000 sporozoites inoculated and the long incubation period was constantly recorded in cases receiving 100 sporozoites. When one mosquito was allowed to feed on volunteers or 1 000 sporozoites were injected, the incubation period may be short or prolonged. CONCLUSIONS: The 48-hour cycle in the infectivity of gametocyte for mosquitoes was demonstrated and the peak of oocyst production preceded the peak of parasitaemia by 1 to 3 days. Prompt radical treatment is extra important. Since the incubation period is variable depending on the number of sporozoites inoculated and the tropical versus temperate zone malaria is not all-inclusive, the classification of tertian malaria might be reconsidered.

Animals↗