Monarch Butterflies and Parasitic OE

We discussed Monarch Butterflies on several occasions and we saw the normal wing anatomy under the microscope. On this occasion I was speaking with a neighbor who was raising butterflies in tents in her back yard. She was happy to rescue the little caterpillars and protect them from predation. She did point out one of the butterflies who was not doing very well. I collected it and brought it home. I had a suspicion that it was ill and was not going to survived. I suspected a protozoan, Ophryocystis elektroschirrha (OE) infection. I baged it and put it in the freezer to euthanize it as recommended.

Featured image is a healthy male monarch butterfly as noted by the two darker spots in the dorsal veins of the tail wings.

GROSS EXAMINATION:

The butterfly was unable to fly and its wings were all crumpled up. It was thrashing about on the ground. Post mortem I photographed the remains which had not changed significantly from the time I found it. It shows a typical irregular wing deformity characteristic of a OE infection.

Newly emerged Monarch Butterfly with distinct symptoms of OE infection.

MICROSCOPIC EXAMINATION:

I placed the specimin in a paper envelop to avoid spreading spores. With rubber gloves and cotton pliers the remains were placed on the stage of the microscope. These are bright field flash illuminated images. I looked for the telltail OE spores on the abdomen and wings. I’m not an expert in insect paracytology and I could be misinterpreting these observations. None-the-less here is what I found.

This 200X magnification of the wrinkled dorsal surface of the Monarch wing with shows scales and pollen. (photoflash exposure)

Another area of the Monarch wing at 100X (photoflash exposure)

This is a sample of scrapings from the abdomen and underside of the Monarch wings magnified to 400X (bright field transmitted light). There is no sign of spores.

Using the microscope I also examined the envelop that held the remains and found no sign of OE spores.

RESULTS:

Without evidence of spores my suspicion remains the same. This still could be a OE parasite infection based on behavior and gross appearance. The spore count could be insufficient to be seen or the infection could be in an early stage. I will continue to look for other Monarchs with similar signs and inspect them for spores. Examination for OE would make an excellent citizen scientist community investigative effort.

I informed my neighbor of my findings and recommended that she follow the recommendations of Project Monarch Health. This site is readily available to all readers who enjoy observing these beautiful creatures. It is especially helpful for the hobbyist who wishes to grow them in their yard in tents.

Here is an extract from https://www.monarchparasites.org/presentations

Illustration from Project Monarch Health.

“In a Nutshell“:

OE is a common and debilitating parasite of monarchs that can cause deformity and even death.
Heavily infected monarchs with clearly visible signs of OE infection (e.g., deformity) should be euthanized by freezing.
Monarchs with lower spore loads can be released, provided that the captive rearing conditions did not foster parasite transmission.
Containers, cages, surfaces and nets that contact adult monarchs should be carefully sanitized with 20% chlorine bleach to kill OE spores and prevent transmission.
Infected monarchs should not be kept as pets (as an alternative to euthanasia), as this will result in high rates of OE contamination to future generations of monarchs reared in the same household.

My general sense is that raising butterflies with good intention of preserving them from predators may in fact put them at a greater risk. Concentrating the insects may promote higher cross contamination. The grossly infected die but when the tent full of Monarchs with low to moderate levels of OE are released they spread the disease through the outside population.

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