xxv MOSQUITOES 313 



colour being due to the presence of the colouring 

 matter of the blood. The presence of haemoglobin in 

 the urine comes about in this way. When cattle an- 

 bitten by the blue tick this arachnid may infect it with 

 the disease-producing parasite known as a piroplasm : 

 these micro-parasites multiply rapidly, invade, and 

 destroy the red corpuscles of the blood. As a result, 

 the red colouring matter (haemoglobin) is excreted with 

 the urine. The remains of the disintegrated corpuscles 

 are retained by the spleen or by the liver, and the 

 disturbance this causes in the latter organ leads to 

 jaundice, which is a clinical feature often present in the 

 late stages of this disease. 



Red-water is a disease widely spread in North 

 and South America, India, China, Queensland, Great 

 Britain, and all over Africa. In South Africa it has 

 been known since 1 870 ; it was imported with oxen 

 from Madagascar (Theiler). Treatment is useless in 

 dealing with the disease, which can only be eradicated 

 by destroying the ticks which transmit it. 



East Coast Fever is a formidable disease, and has 

 caused the deaths of many thousand head of cattle in 

 East Africa : it is due to the entrance of a minute 

 parasite into the red corpuscles of the blood subsequent 

 to infection from the bite of a tick, but the parasites 

 do not lead to the destruction of the corpuscle. In 

 this disease peculiar bodies are found in the lymph 

 ulands and spleen, known as Koch's granules, which are 

 regarded as characteristic of East Coast Fever. The 

 transmitter of this disease is a brown tick belonging to 

 the group Rhipicephalidae : this tick is widely dis- 

 tributed in South and East Africa. 



The difficulty of eradicating this disease may be 

 appreciated when we realise " that one infected tick is 

 capable of transmitting it." 



Mosquitoes are blood-sucking insects, and a constant 

 source of annoyance to human beings, for their bites are 

 irritating and in some instances dangerous to health and 



