WJEC Biology for A2: Student Bk

Neuraminidase 1 2 Haemagglutinin 1 Spanish ’Flu 1918; Swine ’Flu 2009 Endemic in humans, pigs, birds 2 Asian ’Flu 1957 3 Hong Kong ’Flu 1968 5 Bird ’Flu 2004 Malaria ▪ Malaria is caused by a protoctistan, Plasmodium . There are five species which cause malaria, but P. falciparum causes the most deaths. P. vivax is also a major killer. ▪ Plasmodium is transmitted by over 100 species of Anopheles mosquitos, when they pierce the skin to take a blood meal. The females are vectors of malaria but the males are not, as they feed on plant nectar, not blood . ▪ Malaria occurs in habitats that support the Anopheles mosquito. ▪ Malaria: – Is endemic in some sub-tropical regions. – Can become epidemic during wet seasons. – Can also be regarded as pandemic. It affects millions of people worldwide and kills more people than any other infection, despite the years of research and drug development. The transmission of malaria ▪ When a mosquito takes blood from an infected person, it takes in the sexually reproducing stage of Plasmodium called gametocytes. They produce zygotes, which develop into an infective stage, called sporozoites. Sporozoites migrate from the mosquito’s gut to its salivary glands. ▪ When the mosquito takes another blood meal, Plasmodium sporozoites in the mosquito’s saliva are injected into the human. They travel to the liver and reproduce asexually in the liver cells, producing merozoites. ▪ Merozoites are released into the blood and infect red blood cells, where they do more asexual reproduction. ▪ The red blood cells burst and release more merozoites, which infect more red blood cells. This cycle repeats every few days, and when the red blood cells burst, the fever recurs. ▪ Some merozoites become gametocytes. Examtip At A Level, you will not be tested on the names of the stages of the life cycle of Plasmodium . Going further As global temperatures increase, malaria is already occurring at higher latitudes. It is feared that the mosquitos may survive in places that were previously unsuitable and that malaria will spread. Key Term Vector : A person, animal or microbe that carries and transmits an infectious pathogen into another living organism. Gametocytes in gut FEMALE ANOPHELES MOSQUITO HUMAN sexual stage Sporozoites in salivary glands Asexual reproduction of sporozoites in liver Asexual reproduction of merozoites in red blood cells Merozoites in liver cells Gametocytes in blood The life cycle of Plasmodium Option A: Immunology and disease 265