Mosquito species diversity and abundance in relation to riceland agroecosystem and filarial infection in Kafr El-Sheikh Governorate, Egypt

The present work studied the mosquitoes abundance, identification, distribution and density in three villages [rural area] and one city [urban area] in Kafr El-Sheikh Governorate namely; Kebreet, Minyat Al-Ashraaf, El-Salmia and Fowa city, respectively during the rice cultivation season in relation to filaria from June to Oct. 2009. A total of 11381 mosquitoes larvae belonging to four genera and 8 species were collected. Of which 3525 [31.0%] in Minyat Al-Ashraaf followed by 3339 [29.3%] in Kebreet, 3331 [29.3%] in El-Salmia villages compared with 1186 [10.4%] in Fowa city. The five most common species collected during this study were Culex pipiens [39.2%], Cx. antennatus [27.3%], Cx. univittatus [15.8%], Anopheles pharoensis [10.4%], and An. coustani[3.8%]. The mosquito species diversity [H] and evenness [EH] in the [rice cultivated areas] Minyat Al-Ashraf, Kebreet and El-Salmia villages [H = 1.286, EH= 0.829; H= 1.227, EH= 0.742; H= 1.110, EH=0.882; respectively] were much higher than in the Fowa city [non rice cultivated area] [H= 0.718, EH= 0.608]. On the other hand, the highest diversity and density of adult mosquitoes species obtained from Minyat Al-Ashraaf were 5 species and [33.8%], followed by Kebreet 5 species and [31.6%], El-Salmia 4 species and [24.5%], respectively compared with 3 species and [10.1%] in Fowa city. Cx. pipiens adults were the predominant species, in all filarial indicator areas [68.1, 53.4, 40.8 and 20.8 mosquitoes/room] in Minyat Al-Ashraaf, Kebreet, El-Salmia villages and Fowa city, respectively. Cx. pipiens was the only species to cany infective larvae as well as other stages, while Cx. antennatus carried immature stages only [not infective]. Filarial larvae in Cx. pipiens and Cx. antennatus were found only in Minyat Al-Ashraaf and Kebreet villages. It is inferred from the data that different levels of habitat with regard to rice cultivation have different effects on mosquito diversity and abundance. Also, our study revealed that filarial vectors Cx pipiens and Cx. antennatus had a wide distribution and high relative density especially in irrigated rice regions and hence its role in disease transmission in Kafr El-Sheikh region needs further investigation

Malayan filariasis in Central Sulawesi (Celebes), Indonesia.

Seven villages in Central Sulawesi were surveyed in September 1971 and finger blood samples from 3,658 persons examined for microfilariae. Periodic, nocturnal Brugia malayi was endemic in all seven villages with microfilarial rates (Mf-rate) of 10-42% (av. 25%). The median microfilarial density (MfD50) averaged 5.4 and varied from 0.8 to 9.4 microfilariae per 20 microliter of blood. Males had higher Mf-rate and MfD50 value than females and in males Mf-rates and MfD50 values increased with age. In the female population, however, neither Mf-rates or MfD50 values varied significantly with age. Clinical manifestations of filariasis were found in 12% of 2,412 persons examined and only 2% had elephantiasis. Clinical signs of disease with the exception of elephantiasis, showed good correlations with Mf-rates but not with MfD50 values. Transmigrants experienced clinical manifestations of filariasis earlier and more often than the indigenous population.

Filariasis in West Kalimantan (Borneo), Indonesia.

A survey was carried out among persons residing in 8 villages in the Province of West Kalimantan, Indonesia to determine the prevalence of filariasis. Finger tip blood smears were obtained at night from over 3,000 people and microfilariae of Brugia malayi were found in 108 (3.5%) and Wuchereria bancrofti in 10 (0.3%). Most B. malayi (96 carriers) was found in Kakap, a village near the coast, 20 km from the provincial capital of Pontianak. Nine of 10 cases of W. bancrofti were located in Pahauman, a village 130 km northeast of the provincial capital. Periodicity studies indicate the strain of B. malayi to be subperiodic. In Kakap 18% of 226 persons examined had a clinical history of filariasis and elephantiasis was seen in 13%. This is the first report of rural bancroftian filariasis in the area. A few Mansonia species of mosquitoes were examined but none were infected with filarial larvae.

Observation on the reduction of the prevalence of malayan filariasis in Chumphon Province of South Thailand.

Further studies on malayan filariasis were made at Bangluke canton of Chumphon province of South Thailand, where mass drug treatment was not applied. It was found after 9 years that there was a marked reduction in filariasis in the area. The filariasis infection rate being decreased from 14.1 to 1.9 per cent, the microfilarial rate from 10.8 to 0.9 per cent, and the elephantiasis rate from 3.3 to 1.0 per cent, and the mean microfilarial density among positive cases being decreased from 27.6 to 6.6 per 20 c.mm blood. Dissection of 1,893 Mansonia mosquitoes revealed the finding of only stage I and stage II larvae of B. malayi in seven M. annulifera and M. indiana. The reduction in the filariasis infection was assumed to be due to the interruption of transmission of filariasis cycle in the mosquitoes resulting from DDT spraying operation of the Malaria Eradication Programme of the Thai Government. There were also some positive cases moving out of the area. The rural development programme of the Thai Government also played another important role in the reduction in the prevalence of malayan filariasis in this area.

Vector control of filariasis in the Solomon Islands.

In Solomon Islands, filariasis is caused by the nocturnally perodic form of Wuchereria bancrofti and is transmitted by the same vectors of malaria. This study explores the control of this disease as an additional effect of the Malaria Eradication Programme.