The nematode (roundworm) Angiostrongylus (=Parastrongylus) cantonensis, also called the rat lungworm, is a common cause of human eosinophilic meningitis (neural angiostrongyliasis) and occasionally ocular disease.
Angiostrongylus costaricensis is the causal agent of abdominal angiostrongyliasis and is discussed here.
Learn more about Angiostrongylus cantonensis in this new motion graphic video.
A. cantonensis is known to use multiple rat species as definitive hosts, including black rats (Rattus rattus), brown rats, (Rattus norvegicus), and cotton rats (Sigmodon hispidus). Gastropod (snail and slug) intermediate hosts are numerous and include Achatina spp., Biomphlalaria spp., Bulinus spp., Lymnaea spp., Pomaecea spp., and more. Apart from humans, aberrant infections have occurred in several species of wild and domestic mammals and birds.
Most cases of A. cantonensis-associated eosinophilic meningitis originate from Southeast Asia and Pacific Islands. The parasite has also been reported from Africa, the Caribbean, Australia, Hawaii, and recently the southern United States.
The most notable manifestation of A. cantonensis infection is eosinophilic meningitis caused by the presence of larvae in the brain and resultant local host reactions. Somatic symptoms (e.g. headache, fever, malaise) as well as varying degrees of neurological dysfunction are usually noted. A. cantonensis infection may occasionally prove fatal. Ocular angiostrongyliasis is associated with uveitis, blurred vision, and a substantial loss of visual acuity.
L3 larvae are infective to humans, who serve as incidental hosts. They are around 0.5 mm long, possess a pointed terminal projection on the end of the tail, and may be encased in cuticle (exuviae) molted from previous stages. The following photographs show L3 larvae derived from slug tissues.
Clinical and Morphologic Diagnosis
In eosinophilic meningitis with A. cantonensis, the cerebrospinal fluid (CSF) is abnormal (elevated pressure, proteins, and leukocytes; eosinophilia). On rare occasions, larvae have been found in the CSF or in sections of brain tissue.
The CDC offers a real-time PCR assay for the specific detection of A. cantonensis in human CSF specimens. The CSF should be kept cold (ice packs) and shipped to CDC as soon as possible; alternatively it can be kept frozen until shipment is arranged. Shipment on dry ice is optional. Recommended volume of CSF is at least 2 mL. Volumes less than 1 mL may lead to reduced test sensitivity.
Qvarnstrom Y, da Silva AQA, Teem JL, Hollingsworth R, Bishop H, Graeff-Teixeira C, and da Silva AJ: Improved Molecular Detection of Angiostrongylus cantonensis in Mollusks and Other Environmental Samples with a Species-Specific Internal Transcribed Spacer 1-Based TaqMan Assay. Appl. Envir. Microbiol.; 2010; 76: 5287 – 5289.
Qvarnstrom Y, Sullivan JJ, Bishop HS, Hollingsworth R, da Silva AJ: PCR-based detection of Angiostrongylus cantonensis in tissue and mucus secretions from molluscan hosts. Appl. Environ. Microbiol.; 2007; 73:1415-1419.
Eamsobhanaa P, Limb PE, Solano G, Zhange H, Ganf X, Yongc HS: Molecular differentiation of Angiostrongylus taxa (Nematoda: Angiostrongylidae) by cytochrome c oxidase subunit I (COI) gene sequences. Acta Tropica; 2010; 116: 152–156.
Observe standard universal precautions for handling CSF and other bodily fluids.
Barratt, J., Chan, D., Sandaradura, I., Malik, R., Spielman, D., Lee, R., Marriott, D., Harkness, J., Ellis, J. and Stark, D., 2016. Angiostrongylus cantonensis: a review of its distribution, molecular biology and clinical significance as a human pathogen. Parasitology, 143(9), pp.1087-1118.
Tseng, Y.T., Tsai, H.C., Sy, C.L., Lee, S.S.J., Wann, S.R., Wang, Y.H., Chen, J.K., Wu, K.S. and Chen, Y.S., 2011. Clinical manifestations of eosinophilic meningitis caused by Angiostrongylus cantonensis: 18 years’ experience in a medical center in southern Taiwan. Journal of Microbiology, Immunology and Infection, 44 (5), pp.382-389.
DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.