Cells infected with sporozoites eventually burst, releasing merozoites into the bloodstream. The sporozoites grow and multiply in the liver to become merozoites. After being ingested, the sporozoites within oocysts excyst (i.e., are released) in the small intestine. The human-infective stage are sporozoites from the salivary gland of a mosquito. The oocysts contains up to 4 sporozoites that are bow-shaped. Salivary glands of a single infected mosquito may contain as many as 200,000 sporozoites. Immature sporozoites break through the oocyst wall into the haemolymph. Ookinete forms oocytes from which sporozoites are formed. The oocyst then bursts and sporozoites are released into the body cavity of mosquito. These are the sporozoites the infected tick introduces when it bites an intermediate host. Eventually, the oocyst ruptures and the sporozoites are released into the hemocoel of the mosquito. After the oocyst develops, it ruptures releasing several hundred sporozoites. The average length of the sporozoites is greater than 10 micrometres. The immune system clears the sporozoites from the circulation within 30 minutes. The average length of the sporozoites is less than 10 micrometres.