Hawaii Island, more specifically the Puna District on the east side of the island, has been ground zero for human cases of angiostrongyliasis, or rat lungworm disease for the past 10-15 years. While cases have been reported from other areas of the island, including Kona, and from other islands, including Maui and Oahu, more than 90% of cases originate in the Puna District. Serious cases are occurring at an unacceptable rate and have resulted in death, permanent disability, and loss of income and quality of life. Diagnosis currently involves a spinal tap at a hospital. The total number of cases goes underreported partly due to difficulty and expense of diagnosis, infected visitors returning home, and victims seeking alternative medical treatment.
Puna is a rural, agricultural district, and has the 3rd lowest per capita income level in the state (40% less than the state average in 2000), the 3rd highest unemployment rate, and the highest percentage of families relying on food stamps in the state. According to the US Census (ACS, 2009-2013) of the 41,732 people in the Puna district, 5,241 have no health insurance (12.6%). The district contains 45% of total subdivided lots in Hawaii County (Hawaii Island). From 2000-2010 the population of Puna increased by 66%. Many of the large subdivisions do not have the infrastructure for county water. It is estimated that 75 % of Puna residents rely on rainwater catchment systems for their household use, and it has been shown that catchment water can be a potential source of infection for the disease.
Rat lungworm disease can and has resulted in severe neurological trauma for those individuals having a serious infection. The disease is caused by a parasitic worm, a microscopic nematode, and infection is acquired by ingestion of the worm either from food (raw produce), by water, or potentially from skin contact. The worm requires two different types of hosts; rats, and snails and slugs. Hawaii has 45 established invasive slugs and snail species, all of which are capable of being a host for the parasite, and three invasive rat species. Besides being carriers of disease, invasive snails and rats have a negative impact on agriculture and native plant and animal species, including Hawaii’s endemic snails. Studies have shown invasive slugs and snails to be carrying very high parasite loads, and yet to date no recent control efforts for these hosts have been made by county, state or federal agencies on Hawaii Island.
While the Center for Disease Control states serious cases of angiostrongyliasis are rare, Hawaii Island has had an abnormally large number of serious cases for a relatively small population. The variables thought to be involved in causing this high number of cases are yet to be defined, but may include the high use of catchment systems as a household water source and the establishment of invasive semi-slug populations to Puna in 2004. This slug is a very effective carrier and has an infection rate (over 75%) and its arrival coincides with the increase in the number of cases. More federal funding needs to be delegated for education, to raise public awareness of the disease, for research to determine the factors involved in the high rate of disease incidence, better diagnostic and treatment methods, and for control of invasive snails and rats that carry the disease.