Today I’d like to highlight a question that was recently posed on this blog concerning the use of wild-caught invertebrates as pet food. The writer expressed the well-founded concern that fertilizers might render such invertebrates toxic, and also asked about the possibility of parasite transmission.
Fertilizers might be a concern for invertebrates collected in high use situations, such as insects seined from farm ponds or earthworms taken from golf courses. Frogs in farm ponds are being affected by fertilizers, but likely directly, through water absorption, rather than via diet. I always play it safe and avoid such areas, and I do not collect insects, such as roaches or Japanese Beetles, that are the focus of pest-control campaigns.
Parasite transmission via invertebrates is largely limited to parasites that require 2 hosts in order to complete their life cycle, with the wild-caught invertebrate being the first host and, theoretically, one’s pet being the second.
The most common intermediate (“first”) hosts of “two-host parasites” are crayfishes and snails, although terrestrial invertebrates are also involved (especially earthworms). Fortunately, most such parasites are very specific as regards both hosts, and also must be present in the right stage of their life cycle if they are to infect the second host…the concurrence of these conditions in captivity is, in my experience, highly unlikely.
In general, parasites specific to invertebrates (i.e. a protozoa that attacks one host, such as a cricket) would not be a danger to reptiles or amphibians.
Practices in Zoos
At the Bronx Zoo, wild caught snails and crayfishes have long been used as part of the weekly diet of many turtles and other reptiles without incident. Some zoos do, however, treat these food items in order to kill parasites before using them as food for the animal collection. While many fish medications are lethal to snails and crayfishes, some folks report success with Praziquantel-based products (please write in if you need further information).
In conclusion, there are some risks but, in my experience, these can be easily managed. If your pets will accept dead or tong-fed food items, you might wish to consider using Canned Invertebrates, which are farm-raised and cooked.
Please see my article Wild Caught Insects: Pesticide Concerns for important information on collecting food for your collection.