A critical stage in malaria transmission occurs in the Anopheles mosquito midgut, when the malaria parasite, Plasmodium, ingested with blood, first makes contact with the gut epithelial surface. To understand the response mechanisms within the midgut environment, including those influenced by resident microbiota against Plasmodium, we focus on a midgut bacteria species' intra-specific variation that confers diversity to the mosquito's competency for malaria transmission. Serratia marcescens isolated from either laboratory-reared mosquitoes or wild populations in Burkina Faso shows great phenotypic variation in its cellular and structural features. Importantly, this variation is directly correlated with its ability to inhibit Plasmodium development within the mosquito midgut. Furthermore, this anti-Plasmodium function conferred by Serratia marcescens requires increased expression of the flagellum biosynthetic pathway that is modulated by the motility master regulatory operon, flhDC. These findings point to new strategies for controlling malaria through genetic manipulation of midgut bacteria within the mosquito.

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In view of the worldwide importance of Toxoplasma gondii and Neospora caninum and the limited data on the seroprevalence of these parasites in Egypt, this study aimed to estimate the prevalence of anti-T. gondii and anti-N. caninum antibodies in rabbits, cattle, and humans. We used ELISA methods based on surface antigen 2 of T. gondii (TgSAG2t) and surface antigen 1 of N. caninum (NcSAG1t). High seroprevalence of T. gondii (51.49%) was detected in pregnant women, and antibodies to N. caninum were also detected in human samples (7.92%). Anti-T. gondii or N. caninum antibodies were detected in cattle (TgSAG2t: 10.75%; NcSAG1t: 20.43%). In rabbits, only one sample was N. caninum positive (1.85%). The high prevalence of toxoplasmosis and neosporosis in cattle affects the development of the livestock industry and is also an important infective source for human infection in Egypt.

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Toxoplasma gondii modulates pro-and anti-inflammatory responses to regulate parasite multiplication and host survival. Pressure from the immune response causes the conversion of tachyzoites into slowly dividing bradyzoites. The regulatory mechanisms involved in this switch are poorly understood. The aim of this study was to investigate the immunomodulatory role of T. gondii cyclophilin 18 (TgCyp18) in macrophages and the consequences of the cellular responses on the conversion machinery. Recombinant TgCyp18 induced the production of nitric oxide (NO), interleukin-12 (IL-12), and tumor necrosis factor alpha through its binding with cysteine-cysteine chemokine receptor 5 (CCR5) and the production of gamma interferon and IL-6 in a CCR5-independent manner. Interestingly, the treatment of macrophages with TgCyp18 resulted in the inhibition of parasite growth and an enhancement of the conversion into bradyzoites via NO in a CCR5-dependent manner. In conclusion, T. gondii possesses sophisticated mechanisms to manipulate host cell responses in a TgCyp18-mediated process.