Rat Lungworm

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Overview

Rat (Rattus rattus) eating a native snail in the Hawaiian forest. Photo by Jack JeffreyThe nematode Angiostrongylus cantonensis is a rat lungworm, a zoonotic pathogen which causes a global, emerging infectious disease known as rat lungworm disease (RLWD). This nematode was first discovered in China in 1935 [1], but is now endemic in Asia, Australia, the Caribbean islands and Pacific islands; it has also spread to the American continents with more than 2,800 cases of human infection reported in 30 countries [2, 3]. Rats are the definitive host, primarily Rattus rattus and R. norvegicus [4]. When rats eat infected slugs or snails, they ingest third stage (L3) larvae which eventually grow to sexual maturity and reproduce in the heart [5]. Single-celled eggs hatch in the lung, and first stage larvae migrate up the bronchial tree, are swallowed, and 6-8 weeks after infection are excreted with feces [6]. Slugs or snails then eat rat feces and acquire the first stage larvae. Slugs and snails are obligatory intermediate hosts which support parasite development from the first to the L3 larval stage.

Platydemus manokwari. Photo by R. Hollingsworth, USDAHumans can become infected by ingesting intermediate or paratenic (passive carrier) hosts containing infective L3 larvae. The most important paratenic hosts are crustaceans (such as prawns and land crabs) and predacious land planarians, such as flatworms in the genus Platydemus [7]. Once ingested by humans, larvae penetrate the intestinal mucosa and travel through the liver and lungs to the central nervous system (CNS) [2]. RLWD can be a serious threat to human health. Angiostrongyliasis in humans can result in transient meningitis (inflammation of the meninges of the brain and the spinal cord) or a more serious disease involving the brain, spinal cord and nerve roots, with a characteristic eosinophilia of the peripheral blood and cerebrospinal fluid [8]. Humans are a “dead-end” host, meaning the parasites do not reproduce in humans but remain in the CNS or can move to the eye chamber causing ocular angiostrongyliasis, where they remain until parasite death [3].

A. cantonensis has been documented as a parasitic disease of humans in Hawaiʻi and other Pacific islands since the early 1960’s [9]. semi-slugThe flatworm Platydemus manokwari and the semi-slug Parmarion martensi (hereafter referred to as semi-slug) had recently immigrated to Japan and were thought to be the probable cause of an outbreak of angiostrongyliasis there in the year 2000 [10]. The semi-slug is also a recent immigrant to the Hawaiian Islands [11] and is thought to be responsible for a recent outbreak of angiostrongyliasis cases on the Island of Hawaii [12]. Cuban slug In the district where the disease outbreak occurred (Puna district of the Island of Hawaii), >75% of P. martensi were found to be infected with A. cantonensis. In certain areas, semi-slugs were very numerous and some were heavily infected with L3 A. cantonensis larvae [12]. Please see the current “RLW detection map” on this website for the most recent data on RLW detection in slugs and snails on the Island of Hawaii by the Big Island Rat Lungworm Working Group, College of Pharmacy, University of Hawaiʻi at Hilo.

References

  1. Chen HT. Un nouveau nematode pulmonaire, pulmonema cantonensis, NGN sp. Des rats de Canton. Ann Parasit Hum Comp 1935;13:312.
  2. Wang QP, Lai DH, Zhu XU, Chen X-G, Lun ZR. Human angiostrongyliasis. Lancet Infect Dis 2008;8:621-630.
  3. Wang QP, Wu ZD, Wei RL, Owen ZR, Lun ZR. Human Angiostrongylus cantononsis: an update. Eur J Clin Microbiol Infect Dis 2011;DOI 10.1007/s10096-0111328-5.
  4. Martin-Alonso A, Foronda P, Quispe-Ricalde MA, Feliu C, Valladares B. Seroprevalence of Angiostrongylus cantonensis in Wild Rodents from the Canary Islands. PLoS ONE 2011;6(11): e27747. doi:10.1371/journal.pone.0027747
  5. Alicata JE, Jindrak K. Angiostrongylosis in the Pacific and Southeast Asia. Charles C. Thomas, Springfield, Illinois. 1970.
  6. Wu GH. Angiostrongylus cantonensis. In: Tang JQ ed Nature-borne diseases Science Press Beijing p 1182. 2006.
  7. Hollingsworth RG, Cowie RH. Apple snails as disease vectors, pp. 121-132. In R. C. Joshi & L. S. Sebastian, Eds. Global Advances in Ecology and Management of Golden Apple Snails. Nueva Ecija: Philippine Rice Research Institute. 2006.
  8. Kliks MM, Palumbo NE. Eosinophilic meningitis beyond the Pacific basin: the global dispersal of a peridomestic zoonosis caused by Angiostrongylus cantonensis, the nematode lungworm of rats. Soc Sci and Med 1992;34:199-212.
  9. Wallace GD, Rosen L. Studies on eosinophilic meningitis V. Molluscan hosts of Angiostrongylus cantonensis on Pacific Islands. Am J Trop Med Hyg 1969;18:206-216.
  10. Asato R, Taira K, Nakamura M, Kudaka J, Itokazu K, Kawanaka M. Changing epidemiology of angiostrongyliasis cantonensis in Okinawa Prefecture, Japan. Jpn J Infect Dis 2004; 57:184-186.
  11. Cowie RH. Catalog and bibliography of the nonindigenous nonmarine snails and slugs of the Hawaiian Islands. Bishop Museum Occasional Papers 1997;50:1-66.
  12. Hollingsworth RG, Kaneta RK, Sullivan JJ, Bishop HS, Qvarnstrom Y, da Silva AJ, Robinson DG. Distribution of Parmarion cf. martensi (Pulmonata: Helicarionidae), a new semi-slug pest on Hawaii Island, and its potential as a vector for human angiostrongyliasis. Pacific Sci 2007;61:457-468.