In vivo efficacy of pyrantel pamoate as a post-exposure prophylactic for rat lungworm (Angiostrongylus cantonensis)

Authors: JACOB, J. - University Of Hawaii; STEEL, A. - University Of Hawaii; KALUNA, L. - University Of Hawaii; HESS, S. - Animal And Plant Health Inspection Service (APHIS); LEINBACH, I. - Animal And Plant Health Inspection Service (APHIS); ANTAKY, C. - Animal And Plant Health Inspection Service (APHIS); SUGIHARA, R. - Animal And Plant Health Inspection Service (APHIS); Hamilton, Lindsey; Follett, Peter; HOWE, K. - University Of Hawaii; JACQUIER, S. - University Of Hawaii; WONGWIWATTHANANUKIT, S. - University Of Hawaii; JARVI, S. - University Of Hawaii

Submitted to: International Journal for Parasitology: Drugs and Drug Resistance
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2022
Publication Date: 4/15/2022
Citation: Jacob, J., Steel, A., Kaluna, L., Hess, S., Leinbach, I., Antaky, C., Sugihara, R., Hamilton, L.J., Follett, P.A., Howe, K., Jacquier, S., Wongwiwatthananukit, S., Jarvi, S. 2022. In vivo efficacy of pyrantel pamoate as a post-exposure prophylactic for rat lungworm (Angiostrongylus cantonensis). International Journal for Parasitology: Drug and Drug Resistance. 19:1-5. https://doi.org/10.1016/j.ijpddr.2022.04.002.
DOI: https://doi.org/10.1016/j.ijpddr.2022.04.002

Interpretive Summary: Rat lungworm is a human pathogenic nematode and the leading cause of eosinophilc meningitis worldwide. This parasite in contracted mainly via ingestion of infected snails or slugs in raw or partially cooked produce, especially leafy greens. Hawaii island is currently a hot spot for rat lungworm disease. In vivo studies in rats showed that administering the antihelmintic Pyrantel pamoate (an over-the-counter dog dewormer) within 8 hours after infection significantly reduced the worm burden found in heart and lung tissue at 6 weeks by 53-72%. Pyrantel pamoate may be an effective post-exposure prophalactic for patients to reduce infection and potentially the severity of symptoms.

Technical Abstract: Rat lungworm (Angiostrongylus cantonensis) is a neurotropic nematode, and the leading cause of eosinophilic meningitis worldwide. The parasite is usually contracted through ingestion of infected gastropods, often hidden in raw or partially cooked produce. Pharmaceutical grade pyrantel pamoate was evaluated as a post-exposure prophylactic against A. cantonensis. Pyrantel pamoate is readily available over-the-counter in most pharmacies in the USA and possesses anthelmintic activity exclusive to the gastrointestinal tract (GIT). Administering pyrantel pamoate immediately after exposure should theoretically paralyze the larvae in the GIT, causing the larvae to be expelled via peristalsis without entering the systemic circulation. Pyrantel pamoate was orally administered to experimentally infected rats (11 mg/kg) at 0, 2-, 4-, 6-, or 8-hours post-infection. The rats were euthanized 6 weeks post-infection, and worm burden was evaluated from the heart-lung complex. This is the first in vivo study to evaluate its efficacy against A. cantonensis. This study demonstrates that pyrantel pamoate significantly reduced worm burden by 53-72% (P=0.004), along with the potentially associated severity of infection. This paralyzing effect of pyrantel pamoate may also be beneficial for delaying the establishment of infection until a more suitable anthelmintic such as albendazole is made available to the patient.