Malaria prophylaxis against hypnozoites

Malaria prophylaxis against hypnozoites

P. vivax and P. ovale have a dormant stage called the "hypnozoite"

• hypnozoite remains dormant for months and then "wakes up" to develop into a liver schizont
• the dormant hypnozoite explains why attacks of vivax or ovale malaria can occur long after the end of chemoprophylaxis. This is not due to drug failure, as none of the prophylactic drugs currently advised acts against the hypnozoite stage of P. vivax or P. ovale

Primaquine is active against hypnozoites (present only in P. vivax and P. ovale) and is used in the treatment of these forms of malaria. It also has causal prophylactic activity against the liver stage schizonts of all malaria parasites of humans

Primaquine is occasionally used for terminal prophylaxis, also known as presumptive anti-relapse therapy (PART), to eradicate hypnozoites of P. vivax and P. ovale. However, the routine use of primaquine for prophylaxis or terminal prophylaxis is not recommended (1)

Primaquine is not licensed in the UK and practitioners considering the use of primaquine as a prophylactic agent should consult an expert centre

Primaquine is an oxidant drug and can lead to significant haemolysis in G6PD-deficient individuals.

Reference:

1. UK Health Security Agency. Malaria prevention guidelines for travellers from the UK. April 2025 (online)