Posted by Dr Katy Taylor on 25th April 2016
Prevention and human studies hold the key to malaria elimination
Ineffective animal experiments are hindering malaria vaccine development
Today is World Malaria Day, an annual global day for malaria education and awareness. This year’s theme, “end malaria for good” is based on a new strategy published by the World Health Organisation (WHO), which aims to reduce malaria cases by at least 90% by 20301.
Malaria is caused by parasites that are transmitted by the bite of infected mosquitos. In 2015, there were approximately 214 million new cases of malaria and 348,000 deaths, mainly in sub-Saharan Africa2.
Malaria experiments in animals are notoriously unreliable, which could explain why the main focus of the WHO strategy is on preventative measures. A combination of insect control methods, epidemiology studies and anti-malarial drugs has already shown to dramatically reduce the incidence of malaria.
Sadly however, scientists are continuing to use animals in experiments with the hopes of developing a vaccine against the disease. In 2015, we uncovered cruel research on owl monkeys being carried out by researchers from the University of Oxford and the US Navy. They were injected with a potential vaccine before being ‘challenged’ with the malaria-causing parasite3. Almost all of the animals in the unvaccinated ‘control’ group required life-saving treatment to control the levels of parasites in their blood and prevent anaemia.
Genetically modified mice, and more recently ‘humanised’ mice, are also widely used to test potential malaria vaccines.
Despite over 50 years of malaria research and countless human trials of vaccines that ‘worked’ in animals, no single animal experiment has been able to accurately replicate the human illness and no reliable vaccine exists.
It was recently announced that a vaccine that has been under development by GlaxoSmithKline for almost 30 years has finally been approved as a ‘complementary intervention’ to the recommended prevention strategies for malaria. However the vaccine, known as RTS,S/AS01, is not nearly as ground-breaking as scientists hoped. It has only shown to be 27% effective in young babies and is not able to protect them from severe malaria4.
Instead of advancing medical progress, some experts warn that animal experiments could actually be hampering the development of new vaccines. Jean Langhorne, immunopathologist at the Medical Research Council in London said, “The mouse models have not been very predictive. They’re very good at telling us what vaccines don’t work, but not very good at telling us what vaccines should work”5.
A recent review found that there is a general consensus among malaria researchers that more funding and focus on alternative methods is needed6.
- Global technical strategy for malaria, 2016-2030. (2015). World Health Organisation: http://apps.who.int/iris/bitstream/10665/176712/1/9789241564991_eng.pdf?ua=1&ua=1
- A PfRH5-Based Vaccine Is Efficacious against Heterologous Strain Blood-Stage Plasmodium falciparum Infection in Aotus Monkeys. (2015). Cell & Host Microbe, 17: 130-139. Original article can be found here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4297294/
- Questions and answers on malaria vaccines. (2016). WHO: http://www.who.int/immunization/research/development/malaria_vaccine_qa/en/
- Better animal models needed for malaria vaccine development, experts say. (2011). Nature Medicine, 21 Oct: http://blogs.nature.com/spoonful/2011/10/better_animal_models_needed_fo_1.html
- The relevance of non-human primate and rodent malaria models for humans. (2011). Malaria Journal, 10:23. Original article can be found here: https://malariajournal.biomedcentral.com/articles/10.1186/1475-2875-10-23