Orientia tsutsugamushi
"O. tsutsugamushi" causes a complex and dangerous infection scrub typhus. Infection starts when chiggers bite on the skin during their feeding. The bacteria are deposited at the site of feeding (inoculation), where they multiply. They cause progressive tissue damage (necrosis). Necrosis progresses to inflammation of the blood vessels called vasculitis. This in turn causes inflammation of the lymph nodes, called lymphadenopathy. Within a few days, vasculitis extends to various organs including liver, brain, kidney, meninges and the lung. The disease is responsible for nearly a quarter of all the febrile (high fever) illness in endemic areas. Mortality in severe case or due to improper treatment or misdiagnosis may be as high as 30-70%. About 6% of infected people die untreated, and 1.4% of the patients die even with medical treatment. Moreover, death rate can be as high as 13% where medical treatment is not properly handled. In cases of misdiagnosis and failure of treatment, systemic complications rapidly develop including acute respiratory distress syndrome, acute kidney failure, encephalitis, gastrointestinal bleeding, hepatitis, meningitis, myocarditis, pancreatitis, pneumonia, septic shock, sub-acute thyroiditis, and multi-organ dysfunctions. Harmful symptoms involving multiple organ failure and neurological impairment are difficult to treat, and can be lifelong debilitation or directly fatal. The central nervous system is often affected and result in various complications including cerebellitis, cranial nerve palsies, meningoencephalitis, plexopathy, transverse myelitis, neuroleptic malignant syndrome, and Guillan-Barré syndrome. Death rates due to complications can be up to 14% in brain infections, and 24% with multiple organ failure. It is the major cause of acute encephalitis syndrome in India, where viral infection Japanese encephalitis has been regarded as the main factor.
Myrmecia (ant)
Fatalities associated with "Myrmecia" stings are well known, and have been attested to by multiple sources. In 1931 two adults and an infant girl from New South Wales died from ant stings, possibly from "M. pilosula" or "M. pyriformis". Another fatality was reported in 1963 in Tasmania. Between 1980 and 2000, there were six recorded deaths, five in Tasmania and one in New South Wales. Four of these deaths were due to "M. pilosula", while the remaining two died from a "M. pyriformis" sting. Half of the victims had known ant-sting allergies, but only one of the victims was carrying adrenaline before being stung. Most victims died within 20 minutes of being stung, but one of the victims died in just five minutes from a "M. pyriformis" sting. No death has been officially recorded since 2003, but "M. pilosula" may have been responsible for the death of a man from Bunbury in 2011. Prior to the establishment of a desensitisation program, "Myrmecia" stings caused one fatality every four years.