Atypical hyperpachymorph Trypanosoma (Nannomonas) congolense forest-type in a dog returning from Senegal

Trypanosoma congolense forest-type was identified by PCR in France, in a dog returning from Senegal. This paper describes the morphological features of the parasite on Giemsa-stained smears. Slender forms and “latent bodies” represent 30.4% and 20.4%, respectively. Some rosettes have been observed (0.8%). The predominant form (48.4%) is stumpy, close to “montgomeryiform”, but it is unusually broad, with a width/length ratio (WLr) of 0.40-0.55, while that of “montgomeryi-forms” is close to 0.3. To the best of our knowledge, this is the first description of such a form of T. (Nannomonas). Also unusual, the shape of the cytoplasm appears to be tightened by an “S-” or “C-” shaped flagellum. We propose naming this peculiar morphotype “hyperpachymorph”, and adding its description to that of T. congolense forest-type. Thus T. (Nannomonas) forms would include: sphaeromorph or “latent bodyform” (globular), hyperleptomorph (rodhaini-form, very long and slender, with a free flagellum); leptomorph (simiae-form, slender, with a free flagellum); isomorph (congolense-form, short, generally without a free flagellum); pachymorph (montgomeryi-form, short and stout; 0.25 < WLr < 0.34, without a free flagellum), and hyperpachymorph (“hyper-montgomeryi-form”, short and very stout; 0.35 < WLr < 0.7, without a free flagellum).