Seasonal variations in human onchocerciasis transmission by black flies (&lt;i&gt;Simulium damnosum&lt;/i&gt; s. l.) in a forest area of Cross River State, Nigeria

Atting, I; Ejezie, G. C.; Braide, Eka I.; Opara, Kenneth Nnamdi; Ekwe, Asuquo

doi:10.4314/ajazeb.v7i1.41139

Cited by 6 publications

(11 citation statements)

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“…The low temperatures during rainy periods might also impede the development of the Simulium larvae. However, results from this study are divergent to findings by Atting et al [28] and Opara et al [29] in Nigeria reporting that the number of S. damnosum increased during periods when rainfall was at its peak. Opara et al [29] suggested that the increase in fly abundance may be due to the increase in oxygen in the breeding habitats, rivers and streams [29].…”

Section: Discussioncontrasting

confidence: 99%

Biting rates and relative abundance of Simulium flies under different climatic conditions in an onchocerciasis endemic community in Ghana

et al. 2020

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Background: Knowledge of the relative abundance and biting rates of riverine blackflies (vectors of onchocerciasis) is essential as these entomological indices affect transmission of the disease. However, transmission patterns vary from one ecological zone to another and this may be due to differences in species of blackfly vectors and the climatic conditions in the area. This study investigated the effects of climate variability on the relative abundance and biting rates of blackflies in the Tanfiano community (Nkoranza North District, Bono East Region, Ghana). Such information will help to direct policy on effective timing of the annual mass drug administration of ivermectin in the area. Methods: The study employed human landing collections and locally built Esperanza window traps to collect blackflies from March 2018 to February 2019. The relative abundance and biting rates of the Simulium vectors as well as the monthly climatic conditions of the study area were monitored. Correlation analysis and Poisson regression were used to establish the relationships between the variables. Results: The relative abundance and biting rates of the Simulium vectors were highest in the drier months of March, April and August, characterized by high temperatures, low humidity, longer hours of sunshine and stronger winds. The rainy months of May, June and July, characterized by low temperatures, high humidity, few hours of sunshine and weaker winds, had relatively low blackfly abundance and biting activity. Correlation analysis showed that only temperature was significantly, positively correlated with the relative abundance of blackflies (r = 0.617, n = 12, P = 0.033) and monthly biting rates (r = 0.612, n = 12, P = 0.034). A model to predict relative abundance and monthly biting rates using climatological variables was developed. Conclusions: This study demonstrated that Simulium species in the study area preferred higher temperature, lower humidity and rainfall, more hours of sunshine and relatively stronger winds for survival. It is thus recommended that for the study district and others with similar climatological characteristics, mass drug administration of ivermectin should take place in April and September when the abundance of vectors has begun to decline after peaking.

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Section: Discussioncontrasting

confidence: 99%

Biting rates and relative abundance of Simulium flies under different climatic conditions in an onchocerciasis endemic community in Ghana

et al. 2020

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“…Our observation corroborates earlier observation [2,11]. Immature forms (larvae and pupae) were present in all the months prospection was made.…”

Section: Discussionsupporting

confidence: 82%

“…Since the early reports on the distribution of breeding sites of black flies in Nigeria [2] several other reports have emerged from different ecological zones [9][10][11]. The river systems and large streams descending the Jos plateau are known to support different species of black flies [9,10,12].…”

Section: Introductionmentioning

confidence: 99%

Substrate colonization and relative abundance of immature forms of black flies (Diptera: Simuliidae) in river Mada, Nasarawa State Nigeria

Uzoigwe¹,

Njoku²,

Amuga³

et al. 2013

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Black flies, vectors of Onchocerca volvulus, are known to colonize fast flowing sections of rivers. A study on aspects of ecology of immature forms of black flies was conducted at River Mada. Larvae and Pupae of the Genus: Simulium were prospected on natural substrates found at various water currents along the course of the river over a 12-month period. Larvae of six species and pupae of three species were identified colonizing different substrates in the river. A total of 443 larvae and 142 pupae were collected, and the peak month of collection was April. 405 (91.4%) larvae were identified as S. damnosum sl while 38 (8.6%) comprised S. adersi, S. hargreavesi, S. cervicornotum, S. bovis and S. vorax. 110 (77.5%) of the pupae collected were S. damnosum sl while 32 (22.5%) were S. adersi, and S. hargreavesi. The larvae unlike pupae appeared to be non discriminatory in substrate colonization and current preference. Paucity of the population of immature forms is observed and attributed primarily to scarcity of suitable substrates and other factors also discussed herein.

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“…Acute and chronic a Higher transmission potential in the rainy season when vector abundance and infection is elevated (in Nigeria) [51] Pertussis Acute i and f � Higher incidence June through October (in the US) [52] Plague Acute a, b, c, f, and g The seasonality varies among countries and is dependent on seasonality of reservoir and vector species and in some cases agricultural cycles [53] Poliomyelitis Acute i, c � , and h � Epidemics occurred during the summer (in the US) [6] Rabies Acute b…”

Section: Descriptionmentioning

confidence: 99%

The calendar of epidemics: Seasonal cycles of infectious diseases

2018

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Seasonal variations in human onchocerciasis transmission by black flies (<i>Simulium damnosum</i> s. l.) in a forest area of Cross River State, Nigeria

Cited by 6 publications

References 0 publications

Biting rates and relative abundance of Simulium flies under different climatic conditions in an onchocerciasis endemic community in Ghana

Biting rates and relative abundance of Simulium flies under different climatic conditions in an onchocerciasis endemic community in Ghana

Substrate colonization and relative abundance of immature forms of black flies (Diptera: Simuliidae) in river Mada, Nasarawa State Nigeria

The calendar of epidemics: Seasonal cycles of infectious diseases

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