There is very little published on how a GI protozoa is assessed to be pathogenic in reptiles. Not only that, but the line between commensal and pathogenic is virtually inapparent. There is much conflicting information, but with the number of factors that can come into play, I'm looking for anything that can help create some form of definitions.
Dear Adolf,
the question is to my opinion too complex...
personally, i would be cautious with terms "pathogenic" versus "apathogenic", because, we actually have only little evidence based data (especially from experimental infections) in reptiles; in natural infections, we deal with a lot of coinfections (e.g. bearded dragon with different flagellates, coccidia, cryptosporidia and amoeba); it is difficult to assume the role of each of them in the pathogenesis of disease; furthermore cases are complicated by presence of evtl. bacteria, viruses and helminths...i prefere personally low or e.g. high virulent organisms. why complex?
on the one side, we deal with a lot of different reptile species...so one parasite can be more virulent to some, e.g. Entamoeba invadens for snakes or lizards and less in turtles; there are some evidence that same can be true for flagellates (for Parabasalia like Monocercomonas or Hypotrichomonas; but also diplomonads like Hexamita); e.g. we virtually see no symptoms in tortoises with Parabasalia flagellates, but in some cases in snakes or lizards.
on the other side, to predict some pathogenic role of an organism, we have to know the species or even strain. This is a real problem with e.g. Entamoeba spp., where a fecal diagnostics at species level by molecular tools is still a problem; also in flagallates or some ciliates (of course there are also other protozoa occuring in reptiles...).
with Cryptosporidium, man labs are offering differentiation at species level (usuling by sequencing of 18S rDNA) which is very important, in order to exclude "passing true organism" from prey animals and there are many data now available in literature on pathogenicity...
With coccidia...based on the host specificity, one should consider them individually at species level of the reptile, but there is some evidence that e.g. Isospora can cause diseases e.g. in bearded dragons or chameleons (especially in young animals) based on direct life cycle and accumulation within an enclosure with bad hygiene; same is the case with coccidia infecting the gall bladder as Choleoeimeria; but low virulence is assumed for coccidia with indirect life cycle as e.g. Sarcocystis; also to be excluded are coccidia from pray animals like e.g. Eimeria from rodents/rabbits in snake feces.
With ciliates some are regarded low virulent like Nycthoterus and some as facultative pathogenic like Balantidium.
best regards
Niko
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