Malaria News Today 2020-09-01

Today we feature summaries and abstracts concerning Plasmodium malariae, P. knowlesi and monkey models for vaccine testing, clothianidin insecticide resistance, the mosquito immune system and drug interactions between medicines for malaria patients.

Some mosquitoes already have resistance to the latest weapon against malaria

By Munyaradzi Makoni: An insecticide about to be widely deployed inside African homes to combat malaria-carrying mosquitoes is already losing its punch. Two years ago, the World Health Organization (WHO) gave the green light for clothianidin, long used in agriculture to kill crop pests, to be added to the current mainstays of indoor mosquito control, which are losing their effectiveness as the insects develop resistance. Since then, many African countries have been laying plans to spray the walls of homes with the pesticide—it would represent the first new class of chemicals adopted for such use in decades—and looking anxiously for evidence of pre-existing resistance.

Now, scientists at Cameroon’s Centre for Research in Infectious Diseases (CRID) have found it. They recently sampled mosquitoes from rural and urban areas around Yaoundé, the capital, including two key malaria carriers. In one standard susceptibility assay, exposure to clothianidin for 1 hour killed 100% of Anopheles coluzzii. But in some A. gambiae samples as many as 55% of the mosquitoes survived, the group reported in a preprint posted 7 August on the bioRxiv preprint server.

Atlas of Malaria Mosquitoes’ Immune System Assembled

An international team of scientists led by investigators at the Wellcome Sanger Institute and the NIH has created the first cell atlas of mosquito immune cells to understand how the insects fight malaria, as well as other mosquito-borne infections. The mosquito host is essential for the malaria parasite to complete its lifecycle, so any disruption would dramatically reduce the transmission of one of the world’s deadliest diseases.
Findings from the new study—published recently in Science through an article titled “Mosquito cellular immunity at single-cell resolution“—discussed the discovery of new types of mosquito immune cells, including a rare cell type that could be involved in limiting malaria infection. The authors also identified molecular pathways implicated in controlling the malaria parasite.

Genetic analysis of the orthologous crt and mdr1 genes in Plasmodium malariae from Thailand and Myanmar

Plasmodium malariae is a widely spread but neglected human malaria parasite, which causes chronic infections. The observed polymorphisms in pmcrt and pmmdr1 genes are unlikely to affect protein function and unlikely related to chloroquine drug pressure. Similarly, the absence of pmmdr1 copy number variation suggests limited mefloquine drug pressure on the P. malariae parasite population, despite its long time use in Thailand for the treatment of falciparum malaria.

Quantification of Plasmodium knowlesi versus Plasmodium falciparum in the rhesus liver: implications for malaria vaccine studies in rhesus models

Rhesus macaques are valuable pre-clinical models for malaria vaccine development. The Plasmodium knowlesi/rhesus and Plasmodium falciparum/rhesus models are two established platforms for malaria vaccine testing… Detection of 18S rRNA in the liver following high dose intravenous PfSPZ confirmed that rhesus are modestly susceptible to wild-type P. falciparum sporozoites. However, comparison of 18S rRNA RT-PCR biomarker signal indicates that the P. falciparum liver burden was 3–5 logs lower than in PkSPZ-infected animals. Quantification of this difference in liver stage burden will help guide and interpret data from pre-clinical studies of live-attenuated sporozoite vaccines in rhesus models.

Potential drug–drug interactions associated with adverse clinical outcomes and abnormal laboratory findings in patients with malaria

Hospitalized patients with malaria often present with comorbidities or associated complications for which a variety of drugs are prescribed. Multiple drug therapy often leads to drug–drug interactions (DDIs). The following drug pairs reported the highest frequency of adverse events associated with the interactions; calcium containing products-ceftriaxone, isoniazid–rifampin, pyrazinamide–rifampin, isoniazid–acetaminophen, and ciprofloxacin–metronidazole.

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