Ants and Ticks
The ant bites with its jaws, then doubles up to inject venom via the sting, usually resulting in local pain or itch, with a weal or swelling at the site. Some species of ants possess a sting and venom gland in their tails, as well as powerful jaws. Although only local problems typically result from envenomation, patients allergic to the venom may suffer life-threatening reactions. Stinging ants of the genus Myrmecia (jumper ants and bull ants) represent a hazard in the southern states of Australia due to the relatively high proportion of the population (3-4% estimated from one study) with significant allergy to the venom of these creatures.
These aggressive ant species can inflict a painful sting, injecting venom that causes a burning sensation and subsequent blistering (hence their name). An individual ant can sting multiple times, and sting sites may develop pustules and secondary infection. As is the case with jumper ants and bull ants, some people may also suffer potentially life threatening allergic reactions to the venom. They may attack farm and domestic animals and can destroy some plants and crops. Mature nests may contain as many as 200,000 individuals. These ants have caused significant ecological and economic problems in areas where they have become established, such as the United States, South-East Asia and the Pacific Islands of Guam and Okinawa. Two species of fire ants have been identified in Australia. The tropical fire ant, Solenopsis germinata, is found in the Northern Territory, where it has become established in coastal areas, but has not as yet resulted in significant problems. Late in February 2001, the South American fire ant (Solenopsis invicta) was identified in southern Queensland around Brisbane's south west.
Australian Paralysis Tick (Ixodes holocyclus)
(Photo D. Moorhouse)
The female must feed on blood during each of the three stages of the reproductive cycle, and humans can become unintentional hosts. The tick usually feeds for a period of 4-5 days, during which time the accumulation of toxic saliva in the host may result in progressive motor paralysis. Deaths due to tick poisoning are rare, but at least twenty have been recorded in New South Wales this century. Tick paralysis may case significant losses of livestock and farm animals such as dogs. Another Australian tick, Ixodes cornuatus, may also cause paralysis.
Found in bush areas down the eastern aspect of the continent
This tick contains a toxin in its saliva that may cause progressive paralysis in humans by interference with presynaptic transmission in motor nerves. It may also cause severe allergy in some individuals. Significant illness is more common in children, and may present as difficulty walking or general lethargy, progressing to problems with swallowing and limb or generalised weakness. Older children and adults may present with double or blurred vision followed by progressive weakness and paralysis. Occasionally, paralysis is localised, e.g. Bell's palsy.