JPC SYSTEMIC PATHOLOGY
Signalment: (JPC #CG-5) Adult cynomolgus monkey (Macaca fascicularis)
HISTORY: Incidental finding in an adult cynomolgus monkey (Macaca fascicularis)
HISTOPATHOLOGIC DESCRIPTION: Kidney, with perirenal fibrovascular tissue: Expanding the perirenal fibrovascular tissue, creating numerous cavities (parasite migration tracts), and abutting the renal capsule are several cross sections of a 1mm diameter adult filarid nematodes The nematode is characterized by a smooth 4-5 um cuticle; coelomyarian musculature; low, broad-based lateral chords; a pseudocoelom; a large, glandular, lumenless esophagus; an small intestine lined by uninucleated low cuboidal cells; and a uterus containing 2-3 um microfilaria. Multifocally, surrounding the nematode there is abundant edematous fibrous connective tissue with small caliber vessels (granulation tissue), admixed with hemorrhage, erythrocyte-laden macrophages (erythrophagocytosis), eosinophilic fibrillar material (fibrin), moderate numbers of eosinophils, epithelioid macrophages, fewer lymphocytes, plasma cells, neutrophils, and rare multinucleate giant cells. Diffusely, the renal cortical interstitium is mildly expanded by eosinophilic homogenous material (edema), admixed with low numbers of lymphocytes, plasma cells, and neutrophils. Multifocally within the cortex, lymphatics are markedly ectatic, tubules have attenuated or lost epithelium, and many tubules contain low to moderate numbers of viable and degenerate neutrophils admixed with eosinophilic, proteinaceous material and a small amount of eosinophilic cellular and karyorrhectic debris (granular casts). Multifocally within the subcapsular space are few, up to 500 um in diameter, lymphoid nodules.
Adrenal gland (within fibrovascular tissue): No significant lesions.
1. Fibrovascular tissue, perirenal: Retroperitonitis, eosinophilic and granulomatous, focally extensive, moderate with granulation tissue, hemorrhage and few filarial nematodes, etiology consistent with Edesonfilaria malayensis, cynomolgus monkey (Macaca fascicularis), primate.
2. Kidney: Nephritis, tubulointerstitial, multifocal, mild with cellular casts
ETIOLOGIC DIAGNOSIS: Retroperitoneal edesonfilariasis
CAUSE: Edesonfilaria malayensis
- A 12 to 30cm long, filarid nematode that is often found incidentally in cynomolgus and rhesus monkeys (old world primates)
- Adults may be found free in the abdominal cavity or in subserosal connective tissue of the abdominal (most frequently retroperitoneal) and thoracic cavities
- Females release blood-circulating microfilaria
- Unknown life cycle and intermediate host; blood-sucking arthropods and mosquitoes, are suspected
TYPICAL CLINICAL FINDINGS:
- Clinically healthy
- +/- mild anemia; moderate eosinophilia; and/or hyperproteinemia, with decreased albumin/globulin ratio
- In one case, parasitic emboli led to pulmonary infarction and pneumonia
TYPICAL GROSS FINDINGS:
- Parasites are found free in the peritoneal cavity with thickening of connective tissue, hemorrhage, and adhesions of the serosa involving the site occupied by the filarids
- Splenic nodules have been described in infected cynomolgus monkeys as a secondary lesion specifically related to the infection
- Have also been documented in pulmonary blood vessels, parietal and visceral pleural surfaces and in urinary bladder wall
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Nematode with a “lumenless” glandular esophagus is characteristic
- Coelomyarian musculature, very small intestine (important diagnostic feature of filarids); small lateral chords and may have small internal cuticular ridge at the lateral chords
- Small arteries within associated lesions frequently have intimal thickening and narrowing of lumina in addition to the presence of microfilaria; rarely, there is vasculitis
- Microfilariae (larvae) are also present extravascularly in these lesions and occasionally are engulfed by multinucleate giant cells
ADDITIONAL DIAGNOSTIC TESTS:
- Microfilaria may be identified on blood smears and with the Knott’s test
- Dirofilaria magnilavatum and macacae: Found in the subcutaneous tissues of the trunk and lower extremities
- Brugia malay and B. pahangi: Adults found in the lymphatics and perilymphatic tissues
- Macacanema formosana: Commonly inhabits peritracheal connective tissue and the diaphragm and has similar esophageal morphology to Edesonfilaria malayensis; differentiation based on posterior morphology of intact male worms
Other Old World Monkey filarid nematodes:
- Most of the above listed filarids infect Asian monkeys
- Dirofilaria corynodes: Subcutaneous tissues of the trunk and lower extremities in African monkeys; very little tissue reaction
- Loa papionis: Drills, baboons, mangabeys, and vervets; very similar to loa in humans; infestations asymptomatic
- Meningonema peruzzii: Subarachnoid space along the dorsum of the brain stem at the level of the medulla oblongata in African monkeys
- Experimental infection of Wuchereria bancrofti in the Silvered Leaf monkey has been used as an animal model for human filariasis (elephantiasis)
New World Monkey filarid nematodes:
- Dipetalonema and Mansonella (Tetrapetalonema) sp.: Abdominal or thoracic cavities (fibrinopurulent peritonitis or pleuritis) or in subcutaneous tissues (very little, if any, inflammatory response) Great Apes:
- Onchocerca volvulus: Subcutaneous fibrous nodules in gorillas and humans; microfilaria in the dermis
- Mansonella streptocerca, rodhaini, and M. vanhoofi: Chimpanzees
- Dirofilaria immitis in orangutans
- Loa loa in chimpanzees and gorillas
- Abbott DP, Majeed SK. A survey of parasitic lesions in wild‑caught, laboratory‑maintained primates: Rhesus, Cyanomologus, and Baboon. Vet Pathol. 1984;21:198‑207.
- Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: American Registry of Pathology; 1999:35,39.
- Lowenstine LJ, Osborn KG. Respiratory system diseases of nonhuman primates. In: Abee CR, Mansfield K, Tardif S, Morris T, eds. Nonhuman Primates in Biomedical Research: Diseases. 2. 2nd ed. Oxford, UK: Elsevier; 2012:466.
- Narama I, Miura K, Tsuruta M, et al. Microfilarial granulomas in the spleens of wild‑caught Cynomolgus monkeys. Vet Pathol. 1985;22:355‑362.
- Strait K, Else JG, Eberhard ML. Parasitic diseases of nonhuman primates. In: Abee CR, Mansfield K, Tardif S, Morris T, eds. Nonhuman Primates in Biomedical Research: Diseases. 2. 2nd ed. Oxford, UK: Elsevier; 2012:227,231,241.