JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

September 2025

I-P05

Signalment (JPC# 994833): Cynomolgus macaque (Macaca fascicularis)

HISTORY: None

HISTOPATHOLOGIC DESCRIPTION: Mucosa and haired skin, nares: Multifocally, the mucosal epithelium is ulcerated with occasional replacement by serocellular crust that blends into luminal exudate composed of many sloughed epithelial cells, necrotic neutrophils, abundant mucus, necrotic debris, and hemorrhage with few colonies of mixed bacteria. The adjacent intact epithelium contains numerous intraepithelial tunnels with multiple tangential and cross-sections of adult female and male nematodes that are 100-200 µm diameter and have a 2 µm thick cuticle, paired bacillary bands, polymyarian-coelomyarian musculature, a stichosome esophagus or digestive tract lined by uninucleate cuboidal cells with brush border, and either a testis with sperm or a uterus with larvae. There are rare eggs that are 70µm in diameter, have a 5 µm anisotropic shell and contain a coiled larva. The mucosal epithelium exhibits squamous metaplasia, spongiosis, hydropic degeneration, and transmigrating neutrophils. Multifocally within the subepithelial connective tissue and the dermis, there are numerous perivascular intact and necrotic neutrophils, lymphocytes, plasma cells, fewer eosinophils, and macrophages. Rarely, previously described adult nematodes are within lymphatic vessels. Within the epidermis, there is a focally extensive, mild parakeratotic hyperkeratosis with an intracorneal pustule composed of numerous intact and necrotic neutrophils, necrotic debris, and serum.

MORPHOLOGIC DIAGNOSIS: Mucosa and haired skin, nares: Rhinitis and dermatitis, ulcerative, neutrophilic, and lymphoplasmacytic, multifocal, moderate, with intraepithelial and lymphatic adult nematodes and rare eggs, etiology consistent with Anatrichosoma spp., Cynomolgus macaque (Macaca fasicularis), nonhuman primate.

ETIOLOGIC DIAGNOSIS: Nasal anatrichosomiasis

CAUSE: Anatrichosoma sp.

GENERAL DISCUSSION:

• Anatrichosoma sp. are intraepithelial aphasmid nematodes
• Typically found in the nasal epithelium of Old World and New World monkeys, and great apes; zoonotic
• May result in cutaneous larval migrans of the face and extremities, subcutaneous nodules with edema around the joints of the extremities, and white serpiginous blisters of the palms and soles (cutaneous creeping eruptions)
• Anatrichosoma cynomolgi (A. cutaneum/ A. rhina) is the most common species involved
• Life cycle is undetermined; suspect to be direct.

PATHOGENESIS:

• Epithelial damage predisposes to secondary bacterial infection

LIFE CYCLE:

• Reside in nasal mucosa near basal layer of the skin
• Female worms migrate through squamous epithelium, forming tunnels > depositing embryonated egg > tunnels slough releasing eggs > eggs are found in nasal discharge or rarely swallowed and passed in feces
• Male worms are typically found in the deep subcutis/lamina propria

TYPICAL CLINICAL/GROSS FINDINGS:

• Asymptomatic or only mild inflammation; affected skin is white, dry, and scaly; mild serous nasal discharge may occur
• Cutaneous lesions have serpiginous tracts with subcutaneous foreign body reaction
• White tracks on skin on soled and/or palms of hands and soles of feet
  • +/- cutaneous vesicles or pustules
• Regional lymphadenopathy +/- lymph node rupture

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Nasal mucosal hyperplasia and parakeratosis
• Moderate lymphoplasmacytic and eosinophilic inflammation in lamina propia
• Aphasmid nematode structure:
• Adult worms are small and slender
  • Thick cuticle, stichosome (esophageal gland cells that surround the esophagus), paired bacillary bands (hypodermal bands), polymyarian- coelomyarian musculature
  • Females approximately 300 µm in diameter and males are approximately 100 µm
  • Anatrichosoma sp. and Trichosomoides sp. eggs are unique, containing a fully formed larva
  • Eggs are approximately 50 x 75 µm with a yellow, barrel-shaped, anisotropic shell, have bipolar opercula, and are embryonated or larvated
• Serpentine tracks will contain seropurulent to purulent exudate in early stages of infection with surrounded tissue inflammation

ADDITIONAL DIAGNOSTIC TESTS:

• Eggs may be identified from nasal swab or mucosal or peripheral epidermal scraping; eggs rarely present in fecal samples

DIFFERENTIAL DIAGNOSIS:

• Grossly: cutaneous lesions resemble hookworm larval migration (Ancylostoma sp.)
• Histologically: Presence of a nematode with stichosomes, paired bacillary bands, and bipolar larvated eggs is diagnostic
• Ancylostoma sp. have small lateral double alae
• Capillaria and Trichuris lack larvated eggs
• Filarids (Dipetalonema sp., Onchocerca sp., Dirofilaria sp.) lack stichosomes

COMPARATIVE PATHOLOGY:

• Cat: Few case reports of larval migrans; all cases reported in footpads causing lameness with necrosis, ulceration, and sloughing of multiple pawpads
• Dog: Rare cause of otitis externa and erythematous nodular scaling
• Tree shrew (Tupaia glis): Anatrichosoma ocularis infects cornea and conjunctiva
• Opossum (Didelphis virginiana): Anatrichosoma buccalis infects oral mucosa

Intraepithelial nematodes in animals:

• Trichosomoides crassicauda: Urothelium of rats
• Gongylonema sp. Esophagus of ruminants and nonhuman primates; associated with esophageal squamous cell carcinoma
• Eucoleus boehmi: Nasal mucosa of dogs
• Capillaria xenopodis (Pseudocapillaroides xenopi): Skin of clawed frogs
• Capillaria annulata, Capillaria contorta: Crop and esophagus of birds
• Eucoleus aerophilus (Capillaria aerophilia): Respiratory tract of foxes and other canids
• Strongyloides sp.: Small intestine mucosa of milky tree frog.

REFERENCES:

1. Abee CR, Mansfield K, Tardif S, Morris T. Nonhuman Primates in Biomedical Research Diseases. Vol 2. 2nd ed. San Diego, CA: Academic Press; 2012:201, 229, 245-246, 427, 466, 575.
2. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Wiley Blackwell; 2016:152-153.
3. Caswell JL, Williams KJ. Respiratory System. In: Maxie MG, ed. Jubb, Kennedy & Palmer's Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:483, 502, 585.
4. Fletcher OJ, Abdul-Aziz T. Chapter 7: Alimentary System. In: Abdul-Aziz T, Fletcher OJ, Barns HJ, eds. Avian Histopathology. 4th ed. Madison, WI: Omnipress; 2016:293, 300-301, 341-342.
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8. Matz-Rensing K, Lowenstine LJ. New World and Old World Monkeys. In: Pathology of Wildlife and Zoo Animals. Eds. Terio KA, McAloose D, St. Leger J. San Diego, CA: Elsevier; 2018:368.e10, 343-374.
9. Maudlin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:690.
10. McAloose D, Stalis IH. Prosimians. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, UK: Academic Press; 2018:339.e16.
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