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Background: Tsetse flies (Glossina sp.) are vectors of Trypanosoma brucei subspecies that cause human African trypanosomiasis (HAT). Capturing and screening tsetse is critical for HAT surveillance. Classically, tsetse have been microscopically analysed to identify trypanosomes, but this is increasingly replaced with molecular xenomonitoring. Nonetheless, sensitive T. brucei-detection assays, such as TBR-PCR, are vulnerable to DNA cross-contamination. This may occur at capture, when often multiple live tsetse are retained temporarily in the cage of a trap. This study set out to determine whether infected tsetse can contaminate naïve tsetse with T. brucei DNA via faeces when co-housed. Methodology/Principle findings: Insectary-reared teneral G. morsitans morsitans were fed an infectious T. b. brucei-spiked bloodmeal. At 19 days post-infection, infected and naïve tsetse were caged together in the following ratios: (T1) 9:3, (T2) 6:6 (T3) 1:11 and a control (C0) 0:12 in triplicate. Following 24-hour incubation, DNA was extracted from each fly and screened for parasite DNA presence using PCR and qPCR. All insectary-reared infected flies were positive for T. brucei DNA using TBR-qPCR. However, naïve tsetse also tested positive. Even at a ratio of 1 infected to 11 naïve flies, 91% of naïve tsetse gave positive TBR-qPCR results. Furthermore, the quantity of T. brucei DNA detected in naïve tsetse was significantly correlated with cage infection ratio. With evidence of cross-contamination, field-caught tsetse from Tanzania were then assessed using the same screening protocol. End-point TBR-PCR predicted a sample population prevalence of 24.8%. Using qPCR and Cq cut-offs optimised on insectary-reared flies, we estimated that prevalence was 0.5% (95% confidence interval [0.36, 0.73]). Conclusions/Significance: Our results show that infected tsetse can contaminate naïve flies with T. brucei DNA when co-caged, and that the level of contamination can be extensive. Whilst simple PCR may overestimate infection prevalence, quantitative PCR offers a means of eliminating false positives. Author summary: Tsetse flies (Glossina sp.) are vectors of Trypanosoma brucei parasites that cause human African trypanosomiasis, also known as sleeping sickness. As part of disease surveillance, tsetse can be captured in traps and checked for parasite presence. The molecular screening of disease vectors (such as mosquitoes, ticks and blackflies) for the presence of pathogen DNA has gained popularity in recent years. However, DNA contamination may occur at capture when live vectors are retained for a limited period in a trap cage. To explore this, we conducted experiments, initially with laboratory-reared tsetse and then field-caught tsetse from Tanzania. Our results show that infected tsetse can contaminate uninfected tsetse with T. brucei DNA when retained together in a trap cage, and that the level of contamination can be extensive. Infected tsetse consistently shed T. brucei DNA in their faeces, which in turn contaminates other tsetse. This can produce false-positive results, leading to inaccurate reporting of infection prevalence. These findings impact not only trypanosomiasis surveillance, but may also have ramifications for the xenomonitoring of other vector-borne neglected diseases. Future work should explore whether pathogen DNA contamination routes exist in other vector species and, if so, the methods to mitigate DNA contamination in entomological traps. [ABSTRACT FROM AUTHOR]

Tsetse flies significantly impact public health and economic development in sub-Saharan African countries by transmitting the fatal disease African trypanosomiasis. Unusually, instead of laying eggs, tsetse birth a single larva that immediately burrows into the soil to pupate. Where the female chooses to larviposit is, therefore, crucial for offspring survival. Previous laboratory studies suggested that a putative larval pheromone, n -pentadecane, attracts gravid female Glossina morsitans morsitans to appropriate larviposition sites. However, this attraction could not be reproduced in field experiments. Here, we resolve this disparity by designing naturalistic laboratory experiments that closely mimic the physical characteristics found in the wild. We show that gravid G. m. morsitans were neither attracted to the putative pheromone nor, interestingly, to pupae placed in the soil. By contrast, females appear to choose larviposition sites based on environmental substrate cues. We conclude that, among the many cues that likely contribute to larviposition choice in nature, substrate features are a main determinant, while we failed to find evidence for a role of pheromones.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) extensively N- glycosylates its spike proteins, which are necessary for host cell invasion and the target of both vaccines and immunotherapies. These N- glycans are predicted to modulate spike binding to the host receptor by stabilizing its open conformation and host immunity evasion. Here, we investigated the essentiality of both the host N -glycosylation pathway and SARS-CoV-2 N- glycans for infection. Ablation of host N- glycosylation using RNA interference or inhibitors, including FDA-approved drugs, reduced the spread of the infection, including that of variants B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta). Under these conditions, cells produced fewer virions and some completely lost their infectivity. Furthermore, partial enzymatic deglycosylation of intact virions showed that surface-exposed N- glycans are critical for cell invasion. Altogether, we propose protein N- glycosylation as a targetable pathway with clinical potential for treatment of COVID-19. IMPORTANCE The coronavirus SARS-CoV-2 uses its spike surface proteins to infect human cells. Spike proteins are heavily modified with several N -glycans, which are predicted to modulate their function. In this work, we show that interfering with either the synthesis or attachment of spike N -glycans significantly reduces the spread of SARS-CoV-2 infection in vitro , including that of several variants. As new SARS-CoV-2 variants, with various degrees of resistance against current vaccines, are likely to continue appearing, halting virus glycosylation using repurposed human drugs could result in a complementary strategy to reducing the spread of COVID-19 worldwide.