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ANIMALS AND THEIR ENVIRONMENT 



Human Ho$t 



Mosc[uito Host 



Figure 39.13. Wuchereria bancrofti. Adult worms in human lymphatic tissue (A) 

 release microscopic larvae into the blood (B). If these are taken up by a mosquito 

 (C) they migrate to the thoracic muscle where they metamorphose and grow (D, E, F). 

 The infective stage, F, migrates to the proboscis where it can penetrate into man 

 while the insect is feeding. 



Figure 39.14. Trichinella spiralis. Larvae encysted in muscle (A) mature into in- 

 testinal worms when eaten (D). These give birth to larvae that burrow into the host, 

 encysting in muscle. The natural reservoir is rodents (C) and similar animals which 

 eat their dead (D). Pigs (£) will also eat dead rodents. Furthermore, killed rodents 

 and pig scraps are fed to them in garbage (F). Man can become infected by eating 

 insufficiently cooked meat containing larvae. 



