Biting behaviour, spatio-temporal dynamics, and the insecticide resistance status of malaria vectors in different ecological zones in Ghana.

BACKGROUND: A significant decrease in malaria morbidity and mortality has been attained using long-lasting insecticide-treated nets and indoor residual spraying. Selective pressure from these control methods influences changes in vector bionomics and behavioural pattern. There is a need to understand how insecticide resistance drives behavioural changes within vector species. This study aimed to determine the spatio-temporal dynamics and biting behaviour of malaria vectors in different ecological zones in Ghana in an era of high insecticide use for public health vector control. METHODS: Adult mosquitoes were collected during the dry and rainy seasons in 2017 and 2018 from five study sites in Ghana in different ecological zones. Indoor- and outdoor-biting mosquitoes were collected per hour from 18:00 to 06:00 h employing the human landing catch (HLC) technique. Morphological and molecular species identifications of vectors were done using identification keys and PCR respectively. Genotyping of insecticide-resistant markers was done using the TaqMan SNP genotyping probe-based assays. Detection of Plasmodium falciparum sporozoites was determined using PCR. RESULTS: A total of 50,322 mosquitoes belonging to four different genera were collected from all the study sites during the sampling seasons in 2017 and 2018. Among the Anophelines were Anopheles gambiae s.l. 93.2%, (31,055/33,334), An. funestus 2.1%, (690/33,334), An. pharoensis 4.6%, (1545/33,334), and An. rufipes 0.1% (44/33,334). Overall, 76.4%, (25,468/33,334) of Anopheles mosquitoes were collected in the rainy season and 23.6%, (7866/33,334) in the dry season. There was a significant difference (Z = 2.410; P = 0.0160) between indoor-biting (51.1%; 15,866/31,055) and outdoor-biting An. gambiae s.l. (48.9%; 15,189/31,055). The frequency of the Vgsc-1014F mutation was slightly higher in indoor-biting mosquitoes (54.9%) than outdoors (45.1%). Overall, 44 pools of samples were positive for P. falciparum CSP giving an overall sporozoite rate of 0.1%. CONCLUSION: Anopheles gambiae s.l. were more abundant indoors across all ecological zones of Ghana. The frequency of G119S was higher indoors than outdoors from all the study sites, but with higher sporozoite rates in outdoor mosquitoes in Dodowa and Kpalsogu. There is, therefore, an urgent need for a supplementary malaria control intervention to control outdoor-biting mosquitoes.

Predicting the potential global distribution of an invasive alien pest Trioza erytreae (Del Guercio) (Hemiptera: Triozidae).

The impact of invasive alien pests on agriculture, food security, and biodiversity conservation has been worsened by climate change caused by the rising earth's atmospheric greenhouse gases. The African citrus triozid, Trioza erytreae (Del Guercio; Hemiptera: Triozidae), is an invasive pest of all citrus species. It vectors the phloem-limited bacterium "Candidatus Liberibacter africanus", a causal agent of citrus greening disease or African Huanglongbing (HLB). Understanding the global distribution of T. erytreae is critical for surveillance, monitoring, and eradication programs. Therefore, we combined geospatial and physiological data of T. erytreae to predict its global distribution using the CLIMEX model. The model's prediction matches T. erytreae present-day distribution and shows that parts of the Mediterranean region have moderate (0 < EI < 30) to high (EI > 30) suitability for the pest. The model predicts habitat suitability in the major citrus-producing countries, such as Mexico, Brazil, China, India, and the USA. In the Special Report on Emissions Scenarios (SRES) A1B and A2 scenarios, the model predicts a reduction in habitat suitability from the current time to 2070. The findings show that global citrus production will continue to be threatened by T. erytreae. However, our study provides relevant information for biosecurity and risk assessment.

Climate-induced range shifts of invasive species (Diaphorina citri Kuwayama).

BACKGROUND: The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a destructive, invasive species that poses a serious threat to the citrus industry wherever it occurs. The psyllid vectors the phloem-limited bacteria 'Candidatus Liberibacter americanus' and 'Ca. L. asiaticus', causal agents of the incurable citrus greening disease or huanglongbing (HLB). It is essential to understand which regions and areas are suitable for colonization by ACP to formulate appropriate policy and preventive measures. Considering its biology and ecology, we used a machine learning algorithm based on the MaxEnt (Maximum Entropy) principle, to predict the potential global distribution of ACP using bioclimatic variables and elevation. RESULTS: The model predictions are consistent with the known distribution of ACP and also highlight the potential occurrence outside its current ecological range, that is, primarily in Africa, Asia and the Americas. The most important abiotic variables driving the global distribution of ACP were annual mean temperature, seasonality of temperature and annual precipitation. CONCLUSION: Our findings highlight the need for international collaboration in slowing the spread of invasive pests like D. citri. © 2022 Society of Chemical Industry.