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Investigates the genetic characteristics of a stenogamous colony of Anopheles minimus species A in China. Copulation characteristics of wild-caught mosquitoes; Insemination rate of each generation of the specie; Indication of the tendency of the specie to patroclinus inheritance; Involvement of the Y chromosome in stenogamy.

Summary: Two lines of the Oriental malaria vector mosquito Anopheles dirus species A (Diptera: Culicidae), one fully refractory and one fully susceptible to Plasmodium yoelii nigeriensis (an African rodent malaria parasite), were established after 17 generations of mass selection, followed by single female selection for one or two generations. Prior to selection, the stock colony of An. dirus was 17% refractory. Both lines of An. dirus produced abundant ookinetes that started to invade the midgut within 24 h post-infection, as seen in histological sections. In most of the refractory mosquitoes, oocysts stopped development < 12 h post-invasion, indicating a rapid defence mechanism. Dead P. y. nigeriensis parasites were apparently localized as small melanized spots (2–5 μm) seen in wet preparations of mosquito midguts dissected 5–7 days post infective bloodmeal. In some refractory An. dirus females, apart from the spots, a small number of totally encapsulated oocysts (c. 10 μm) were also present. These larger melanized parasites predominated in a few females: they appeared 2–3 days post-infection as a secondary delayed defence mechanism. The progeny of reciprocal matings between susceptible and refractory lines had ∼50% susceptibility. Backcrosses of F[sub 1] hybrids with susceptible or refractory lines increased or decreased the susceptibility of backcross progeny accordingly. Overall, these results suggest polygenic control of susceptibility to P. y. nigeriensis infection. The refractory line of An. dirus showed normal susceptibility to natural infections of the human malarias P. falciparum and P. vivax from local patients. [ABSTRACT FROM AUTHOR]

The prevalence of the four human malaria parasites was investigated among malaria patients at northern, central and southern towns in Thailand along the border with Myanmar between September 1995 and May 1996. Thin smears obtained from 548 Thai and Burmese patients were reviewed by an acridine orange staining method, and many mixed infections with two to four species, including P. malariae and P. ovale, were detected. These diagnostic results were compared with those by two PCR-based diagnoses, microtitre plate hybridization (MPH) and a nested PCR method, both of which targets the same, species-specific regions in the 18S rRNA genes. In both PCR diagnoses, many P. malariae and P. ovale infections were also detected. Detection sensitivity of P. malariae infection was higher in nested PCR than MPH, and a total prevalence of P. malariae infection estimated by nested PCR reached 24.3% (133/548). In 16 of them, the size of PCR products amplified by the P. malariae-specific primer was about 20-bp shorter than the expected size of 115-bp. Four of 16 possessed two different bands with normal and shorter sizes, suggesting that P. malariae isolates may be separated into two types, and that those with shorter products may be new variant form (s) with a nucleotide deletion in the target region. On the other hand, 21 P. ovale infections (3.8%) were detected by nested PCR, but four of them were MPH-negative because of the sequence variation at the probe region. These results indicated that the prevalence of P. malariae and P. ovale along the Thai-Myanmar border may be substantially higher than previously reported. [ABSTRACT FROM AUTHOR]