Highly efficient dry season transmission of malaria in Thailand

Rosenberg, Ronald; Andre, Richard G.; Somchit, L

doi:10.1016/0035-9203(90)90367-n

Cited by 101 publications

(83 citation statements)

References 12 publications

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“…7 Dry season transmission of malaria has been reported in areas with permanent bodies of water where anophelines develop. 10 Two El Niño Southern Oscillation events (1987 and 1992) occurred during this study, which for Venezuela meant less rain than expected. There was also 1 La Niña event in 1988 in which more rain fell than expected (Figure 2).…”

Section: Discussionmentioning

confidence: 99%

Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.

Barrera¹,

Grillet²,

Rangel³

et al. 1999

The American Journal of Tropical Medicine and Hygiene

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Abstract. We stratified the risk of malaria transmission (Plasmodium vivax) in 35 villages along a coastal range in northeastern Venezuela (51 km 2 ) where the main vector is the mosquito Anopheles aquasalis. After 20 years without local malaria transmission, reinfection of the entire area occurred from May to December 1985 by local (continuous) and jump (discontinuous) dispersal. Epidemiologic, environmental, and vector variables were investigated with the aid of a Geographic Information System. Risk factors for malaria transmission were human population density, proximity to pre-adult mosquito habitats (Ͻ 500 m), and the number of pre-adult habitats nearby. Most inhabitants, immature mosquito habitats, and malaria cases were located at low elevations and on gentle slopes. High prevalence of malaria during the dry seasons was associated with the presence of permanent bodies of water containing An. aquasalis. Occurrence of a La Niña event in 1988 (wet and cool phase of the El Niño Southern Oscillation) triggered malaria transmission to unusually high levels, consolidating infection in the area, and rendering traditional control efforts useless. We recommend tracking malaria persistence per village and associated risk factors as methods to reduce the cost of malaria control programs.A malaria focus is a circumscribed locality situated in a current or former malarious area that includes the epidemiologic factors necessary for malaria transmission. These include a human community, at least 1 source of infection, a vector population, and the appropriate environmental conditions.

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Section: Discussionmentioning

confidence: 99%

Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.

Barrera¹,

Grillet²,

Rangel³

et al. 1999

The American Journal of Tropical Medicine and Hygiene

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“…al. 1987, Rosenberg et al 1990b) and infectivity. Graves et al (1988) noted that the presence of P. falciparum gametocytes appeared to reduce the infectivity of P. vivax gametocytes, but not of P. malariae gametocytes, when either was present simultaneously.…”

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confidence: 99%

Mixed-Species Plasmodium Infections of Anopheles (Diptera: Culicidae)

McKenzie

Bossert

1997

Journal of Medical Entomology

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Mixed-pathogen infections of vectors rarely are considered in the epidemiological literature, although they may occur in nature. A review of published reports shows that many Anopheles species are capable of carrying sporozoites of > 1 plasmodium species, of doing so simultaneously in field conditions, and of acquiring and transmitting these in experimental situations. Mixed-species infections in mosquito populations occur at frequencies greater than or equal to the product of the constituent species prevalences, whereas human populations have apparent mixed-species infections at frequencies less than or equal to their corresponding expected values. We present a model for the accumulation of parasite infections over the lifespan of a mosquito that explains this surplus of mixedspecies infections. However, the expected frequencies of mixed infections on the basis of our model are greater than those found in nature, indicating that the sampling by mosquitoes of Plasmodium species from human malaria infections may not be random. KeywordsAnopheles spp; Plasmodium spp; malaria transmission; parasite ecologyThe Pioneering studies of parasite community dynamics have focused on helminths (e.g., Schad 1963, Kennedy 1975, Holmes 1983, Esch et al. 1990. Recently Dobson (1985Dobson ( , 1990 and Dobson and Roberts (1994) have stressed the role of species life-histories in structuring helminth communities and have extended the general ecological principle that as a constituent species becomes more aggregated in its distribution, the relative importance of interspecific competition declines in its population regulation. Although data on the aggregation of Plasmodium species in Anopheles is essentially anecdotal, its variability indicates that Plasmodium species interactions may warrant more concerted investigation.In mixed-species malaria infections of humans, one of the constituent Plasmodium species typically dominates (e.g., Mayne and Young 1938, Molineaux and Grammicia 1980, Looareesuwan et al. 1987, Fox and Strickland 1989. Cohen (1973) analyzed the epidemiological literature and reported a general deficit of detectable mixed-species infections, associated this deficit with splenomegaly, and inferred an underlying heterologous immunity. Hence, the excess of mixed-species infections found during the Carlo project was unexpected, but it also was interpreted as representing species interactions of predominantly cooperative (Cohen and Singer 1979) or predominantly competitive (Molineaux and Grammicia 1980) character. Richie (1988) emphasized competitive interactions in an evolutionary context, suggesting that co-infections promote antigenic divergence, but also proposed a role for mutual facilitation in the ecological succession of Plasmodium species within a mammalian host.Neither the interactions of pathogen species within vectors or the pathogen sampling processes embodied in human-vector contacts have received much attention in the infectious-disease NIH Public Access (Turell et al. 1984, Paulson et al. 1992, V...

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“…It was possible that low grade fever was so common that it was unnoticed (MACDONALD, 1926) was 37.1%. The prevalence of enlarged spleens, which was generally low, appeared to increase from December to February and then fall (Table S), a pattern similar to that of transmission (ROSENBERG et al, 1990a). Only 3 deaths occurred during the 2 years, all adult males and none attributable to malaria.…”

Section: Resultsmentioning

confidence: 71%

“…The key difference between Asia and Africa may be the rate of incidence (MCGREGOR, 1965): a resident received about 15 sporozoite inoculations per year at Ban Phluang (ROSENBERG et al, 1990a), only 10% of the number received at some African foci (MOLINEAUX & GRAMICCIA, 1980;PAYNE et al, 1976). Long-term, sterile immunity to malaria does not develop naturally and the clinical severity of the disease may be correlated with superinfection; partial chemosuppression of parasitaemia, for example, can reduce both fever and spleen prevalence without diminishing protective immunity (BJORKMAN et al, 1986).…”

Section: Discussionmentioning

confidence: 99%

A stable, oligosymptomatic malaria focus in Thailand

Rosenberg¹,

Andre²,

Ngampatom³

et al. 1990

Transactions of the Royal Society of Tropical Medicine and Hygi

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Blood from most of the 250 residents of a nonmiaratorv farming village in south-eastern Thailand was visually examined for malaria parasites monthly for 2 vears. Nearlv 97% of the oonulation had at least one (median=5) patent Plan&d&m falciparum infection per year; 72% had one due to P. vivax (median=l). This contrasted with a slide positivity rate of 17% calculated from 12 months of passive case detection before the study began. Children l-9 years old had the highest mean monthly prevalence (51%) and highest geometric mean den&v (lo/500 white blood cells) Gf P. falciparum. Fewer ihan half the expected number of mixed infections were found but these were more common at high densities of P. falcifxzrum. Individuals over 19 vears old comnrised 52% of the novulation but accounted for only i8% of P. vivaw a&i 32% of P. falciparum gametocytaemias. Fever rates were marainallv h&her in those below 10 vears old (8%) but oc'curred wyth equal frequency in ihose with patent infections or negative. The spieen rate (89% staee 1) was 24% in those under 15 vears old and 7% in &se older. No malaria mortality was seen.

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Highly efficient dry season transmission of malaria in Thailand

Cited by 101 publications

References 12 publications

Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.

Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.

Mixed-Species Plasmodium Infections of Anopheles (Diptera: Culicidae)

A stable, oligosymptomatic malaria focus in Thailand

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