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Microbiology & infectious diseases

Parasites and prion-CNS

Angiostrongyliasis

Authors: Rubens Rodriguez, M.D., Ph.D., Carlos Graeff-Teixeira, M.D., Ph.D.

Deputy Editor-in-Chief: Patricia Tsang, M.D., M.B.A.

Last author update: 17 August 2023

Last staff update: 14 December 2023

Copyright: 2023, PathologyOutlines.com, Inc.

PubMed search: Angiostrongyliasis

Table of Contents

Cite this page: Rodriguez R, Graeff-Teixeira C. Angiostrongyliasis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/parasitologyangiostrongyliasis.html. Accessed January 15th, 2025.

Definition / general

Angiostrongylid nematodes are intra-arterial parasites from wild rodents that may infect humans, causing eosinophilic meningoencephalitis (Angiostrongylus cantonensis [ACa], also known as the rat lungworm), gastroenteritis and hepatitis (Angiostrongylus costaricensis [ACo])

Essential features

Intense eosinophilic inflammation with granuloma and vasculitis, especially in the intestines, liver and meninges, calls attention to angiostrongyliasis
Abdominal angiostrongyliasis may cause tumoral (inflammatory) intestinal lesions or necrotic congestive lesions and perforation
Cerebrospinal fluid (CSF) eosinophilia is the main feature that leads to suspicion of cerebral angiostrongyliasis
Ingestion of larvae developed in mollusks and freshwater crustaceans (ACa) leads to migration to the central nervous system (ACa, CNS) or to mesenteric blood vessels (ACo)
Angiostrongyliasis is a food borne zoonotic disease
- Elimination of larvae in feces or CSF is hindered by the intense inflammatory reactions, for both ACa and ACo; it is not possible to detect larvae in stools

Epidemiology

There is no clear age or gender susceptibility but like many zoonoses, focal and seasonal (spring / autumn, rainy periods) transmission is the rule (Rev Inst Med Trop Sao Paulo 1991;33:373)
Some case series show a predominance of children and young adults
Infective larvae do not invade skin but they may contaminate food, beverages or untreated water and they also may be ingested after consumption of raw mollusks or freshwater shrimps (ACa)
Endemic areas are Southeast Asia and the Pacific Islands for ACa and the Americas (from southern U.S. to northern Argentina) for ACo (Lancet Infect Dis 2008;8:621, Parasit Vectors 2023;16:155)

Sites

ACa larvae are located inside meningeal blood vessels or are less frequently seen moving freely inside eye chambers; they are usually not found in the CSF
- Late stage migration and maturation to adult worm inside pulmonary arteries (ACa) is extremely rare
ACo adult worms live in the mesenteric artery branches of the ileocecal transition; less frequently, they also may develop inside the liver portal venous system
- Rare ectopic arterial location for ACo worms is possible (e.g., spermatic or lower limb arteries)

Pathophysiology

Antigens secreted or eliminated intravascularly by parasites trigger intense eosinophilic inflammatory reactions
ACo worms release eggs, followed by rapid embryogenesis and development of first stage larvae; in well adapted rodent hosts, these larvae are promptly eliminated with feces but in humans, they are trapped in tissues and are the focus for eosinophilic granulomatous reactions (Parasit Vectors 2023;16:155)
Eosinophilic vasculitis and dead worm debris favor arterial mesenteric thrombosis, leading to focal necrosis and intestinal wall perforation
Subacute slow antigen release may cause huge eosinophilic tissue infiltration and intestinal wall thickening

Clinical features

Pain is the predominant symptom for both angiostrongyliasis infections
Eosinophilic meningitis (ACa) is mainly manifested by severe headache and many other neurological signs and symptoms; from other less specific manifestations, migrating dysesthesias may indicate ACa infection
- Fever and neck stiffness are not always present and encephalitic syndromes are rare but are the main cause for poor outcomes
Abdominal pain, either localized in right lower (ileocolitis) or upper (hepatitis) quadrants, may present as an acute abdominal syndrome, sometimes complicated by peritonitis (perforation) or intestinal obstruction (inflammatory tumoral lesions) caused by ACo infection (Rev Inst Med Trop Sao Paulo 1991;33:373)

Diagnosis

Image examinations may disclose nonspecific tissue thickening; in the meninges for ACa and the intestinal wall for ACo
Meningitis or painful abdominal syndromes, associated with blood / CSF eosinophilia, both provide strong evidence in favor of angiostrongyliasis (Pathogens 2023;12:624)

Laboratory

Hallmark for angiostrongyliasis is eosinophilia detected in the blood (ACo) or CSF (ACa)
Serology is available in reference laboratories which may lack extensive performance evaluation and their results should not be considered confirmatory
DNA detection in serum, tissues (ACo) and CSF (ACa) confirms the etiology but it is also only available in reference centers (Parasit Vectors 2023;16:155, Clin Infect Dis 2021;73:e1594)

Case reports

2 year old boy with abdominal pain, bloody diarrhea, fever and palpable mass (Am J Trop Med Hyg 2022;106:1466)
24 year old man with fever, headache and lower limb paresthesia and weakness (Hawaii J Health Soc Welf 2021;80:40)
32 year old man with ileal perforation and 34 year old woman with pain in the right upper abdominal quadrant, hepatomegaly and hepatic nodular lesions with eosinophilic inflammatory lesions (Rev Inst Med Trop Sao Paulo 2008;50:339)

Treatment

Anthelmintics are not recommended for ACo because they lack evidence of efficacy and the course of the infection is usually short and benign (Parasit Vectors 2023;16:155)
- Careful follow up is necessary for early diagnosis and surgical management of complications (i.e., intestinal obstruction and perforation)
Corticosteroids are the mainstay of treatment for eosinophilic meningitis, especially focused on alleviating headache; although without clearly demonstrated efficacy, albendazole (15 mg/Kg/day, bid, 14 - 21 days) is recommended as an antihelminthic medication (Pathogens 2023;12:624)

Gross description

Eosinophilic meningitis (ACa): according to autopsy studies, the brain and spinal cord are generally normal (Lancet Infect Dis 2008;8:621)
Abdominal angiostrongyliasis (ACo): 2 types of intestinal lesions: i) infarction and ii) segmental thickening or tumoral (especially in the colon); multiple segmental small intestinal lesions may mimic Crohn's disease
Macroscopy of the vermiform appendix is indistinct from bacterial acute appendicitis
Multiple small white nodules may be seen on liver surfaces
If lesions are suspicious, many sections from both the appendix and intestinal lesions should be examined in order to find parasitic structures

Gross images

Contributed by Rubens Rodriguez, M.D., Ph.D.

Colonic pseudotumor

Cecal pseudotumor

Small bowel thickening

Small bowel infarction

Small bowel perforation

Microscopic (histologic) description

Eosinophilic meningitis (ACa): meningeal eosinophilic infiltration, eosinophilic granulomas and brain with cell debris, thrombi and inflammatory cell (Acta Trop 2015;141:46)
Abdominal angiostrongyliasis (ACo): heavy eosinophilic infiltration around vessels of the submucosa and muscularis propria (Parasitol Res 1991;77:606)
Granulomas with eosinophils may be found in the arterial wall or around capillaries and arterioles, sometimes associated with eggs or larvae
Eosinophilic arteritis is a main histopathological feature
Severe eosinophilic infiltration, granulomatous reaction and eosinophilic vasculitis, even in the absence of parasitic structures lead to a high probability of diagnosis of ACo infection
Eggs and larvae are usually located inside capillaries and arterioles of submucosa and muscularis propria with severe granulomatous reaction
Definitive diagnosis is made by finding parasitic structures (adult worms, eggs or larvae) inside vessels, mainly in the submucosa or mesenteric vessels; PCR in formalin fixed paraffin embedded (FFPE) specimens can be helpful (PLoS One 2014;9:e93658)

Microscopic (histologic) images

Contributed by Rubens Rodriguez, M.D., Ph.D.

Arterial thrombosis

Eosinophilic arteritis

Severe eosinophilic infiltration

Vascular granuloma and eosinophils

Granuloma with degenerated egg

Degenerated egg

Eggs and eosinophils

Adult worm inside artery

Degenerated worm

Severe eosinophilic infiltration

Adult worm

Differential diagnosis

Crohn's disease:
- Lesions are in the mesenteric side
- Granulomas are usually not associated with eosinophils and not adjacent to capillaries or arterioles
Hepatitis caused by other agents:
- Without a heavy eosinophilic infiltrate
- Eosinophilic granulomas are not seen

Board review style question #1

A 2 year old child with abdominal pain is diagnosed with acute peritonitis. During surgery, areas of intestinal infarction are detected. Histology findings are shown in the image above. What is the diagnosis?

Abdominal angiostrongyliasis
Ascariasis
Schistosomiasis
Strongyloidiasis
Thrombosis

Board review style answer #1

A. Abdominal angiostrongyliasis. Angiostrongylus worms live inside arteries causing a granulomatous reaction and eosinophilic infiltration. Answers B - D are incorrect because strongyloidiasis, ascariasis and schistosomiasis are not intra-arterial parasites and they are not associated with perivascular or intravascular granulomas or intense eosinophilia. Answer E is incorrect because there is a worm inside the arterial lumen.

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Reference: Angiostrongyliasis

Board review style question #2

A young adult presents with eosinophilic meningoencephalitis and a small meningeal tumor. What main finding would establish the presumptive diagnosis of neuroangiostrongyliasis?

Abscess with intense neutrophilic inflammation
Hemorrhage
Histiocytosis and necrotic granulomas
Mononuclear cellular infiltration
Perivascular intense eosinophilic infiltration

Board review style answer #2

E. Perivascular intense eosinophilic infiltration. Presence of a large number of eosinophils in tissues (especially perivascular) is the single most common feature of angiostrongyliasis (cerebral or abdominal). The other answers are not common. Answer C is incorrect because granulomas are usually not necrotic and are always associated with eosinophilia and surrounding parasite structures. Answer A is incorrect because neutrophilic inflammation is not seen in neuroangiostrongyliasis and bacterially complicated secondary infections are not common (as they are with abdominal angiostrongyliasis). Answer B is incorrect because the hemorrhage is not related to neuroangiostrongyliasis. Answer D is incorrect because the most important inflammatory cells are eosinophils.

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Reference: Angiostrongyliasis

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