Indtoduction - Malaria transmission to mosquitoes

9 important questions on Indtoduction - Malaria transmission to mosquitoes

Why are low-density infections interesting?

1. Many people have them
2. No symptoms & not found with diagnostics

Where do gametocytes hide?

For falciparum (deadliest), gametocyte production largely goes invisible. Evidence has been found that they sequester in the spleen and (predominantly) bone marrow

How do gametocytes sequester in the bone marrow?

At the beginning they are stiff and can't get out of the bone marrow. When they mature, they lose their rigidity and can be flushed out of the bone marrow.
After this, it takes a few days before the gametocytes reach peak infectivity
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Why do you need RNA diagnostics to qualify the stages that can be detected in blood?

Gametocytes have the same DNA as asexual parasites, you with RNA diagnostics, you can detect transcripts that are indicative of gametocytes.

When did they see the first gametocytes appearing after infecting people? And did this differ between the blood stage group and mosquito bite group?

8.5-12 days after injection.
More female than male, because 1 male gametocyte can make 8 male gametes that can find a female

Blood stage group 10-100x higher gametocyte prodution

How can a Ugandan study report 90% of infections coming from asymptomatic cases, while a Cambodian study reports >95% came from clinical cases?

In Africa, there are many asymptomatic infections, but also a much higher parasite density. It takes 10-12 days to become infectious, but symptoms develop quite soon. In a perfect health system, once you get sick, you still have 10 days to go to a health facility before you become infectious. So immunology and health seeking behaviour are important

What is the Entomologic Inoculation Rate?

The number of infected bites per person in a time period

What happens with an increasing density?

The likelihood of infecting the mosquitoes goes up. The proportion of infected mosquitoes also increases, but a weaker association.

How can naturally acquired immune responses affect transmission?

1. You can have immunity that stops the gametocyte development in bone marrow
2. You can have immunity that affects transmission when you start producing antibodies when RBCs are being cleared as the immune system sees antigens. So when female and male gametes are taken up by mosquito, the gametocyte antibodies may recognize the gametes and inhibit their development

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