JPC SYSTEMIC PATHOLOGY

URINARY SYSTEM

January 2024

U-P07 (NP)

 

            

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 1 mm diameter adult filarid nematodes. The nematodes are characterized by a smooth 4-5 µm cuticle; polymyrian-coelomyarian musculature; low, broad-based lateral chords; a pseudocoelom; a large, glandular, lumenless esophagus; a small intestine lined by uninucleated low cuboidal cells; and a uterus containing 2-3 µm microfilaria. Multifocally, surrounding the nematodes there is abundant edematous fibrous connective tissue with small caliber blood 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 µm in diameter, lymphoid nodules.

 

Adrenal gland (within fibrovascular tissue): No significant lesions.

 

MORPHOLOGIC DIAGNOSIS: 1. Fibrovascular tissue, perirenal:  Retroperitonitis, eosinophilic and granulomatous, focally extensive, moderate with granulation tissue, hemorrhage and few filarial nematodes, cynomolgus monkey (Macaca fascicularis), primate.

 

2. Kidney: Nephritis, lymphoplasmacytic and neutrophilic, tubulointerstitial, multifocal, mild with cellular casts. 

 

ETIOLOGIC DIAGNOSIS: Retroperitoneal edesonfilariasis

 

CAUSE: Edesonfilaria malayensis 

 

GENERAL DISCUSSION:

• A 12 to 30 cm 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  

 

PATHOGENESIS:

 

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 and mechanical damage to adjacent tissues (pancreas and iliopsoas).
• Also documented in pulmonary blood vessels, parietal and visceral subserosal connective tissue, retroperitoneal masses and in urinary bladder wall

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Nematode with a lumenless, glandular esophagus is characteristic of this genus
• 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
• Hemorrhage, fibroplasia of connective tissue, granulation tissue and lymphocytic and eosinophilic infiltrates
• Splenic nodules composed of highly vascular large reticuloendothelial cells, reticulum fibers, eosinophils, erythrocytes and microfilariae
• Pumonary infarcts and pneumonia found in one case; likely due to parasitic emboli following ivermectin administration

 

ADDITIONAL DIAGNOSTIC TESTS:

 

DIFFERENTIAL DIAGNOSIS:

• Dirofilaria magnilavatum and D. 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

 

COMPARATIVE PATHOLOGY: 

Other Old World Monkey filarid nematodes: 

• Dirofilaria immitis: Lung lesions related to nematode larval migration within pulmonary vasculature in a rhesus monkey 
• 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 L. 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:

 

Great Apes:

• Onchocerca volvulus: Subcutaneous fibrous nodules in gorillas and humans; microfilaria in the dermis
• Mansonella streptocerca, M. rodhaini, and M. vanhoofi: Chimpanzees
• Dirofilaria immitis in orangutans 
• Loa loa in chimpanzees and gorillas

                                                                              

REFERENCES:

1. Gardiner CH, Poynton SL.  An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: American Registry of Pathology; 1999:35,39.  
2. 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. Vol. 2. 2nd ed. Oxford, UK: Elsevier; 2012:465-466.   
3. 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. Vol. 2. 2nd ed. Oxford, UK: Elsevier; 2012:227,231,241.

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