The “rice” no one wants to eat
Guest Post by Ashley Lackey
Working as a veterinary assistant, I am routinely exposed to what most people would consider disgusting situations. Besides cleaning up fecal matter, and other bodily excretions on a daily basis, I get the chance to take samples of these different fluids and examine them for parasites. A parasite is an organism that lives in or on a host and acquires its nutrients at the expense of the host. Not all parasites make their hosts ill; the number of parasites in a host is often related to the level of severity of the infection.
A cat was brought in to the Pet Hospital, the owner was worried because she had been seeing small worms, she described as “the size of a grain of rice” coming out of her pets rear; the owner stated she would see these little grains of rice all around the house especially where the cat would take her naps.
After speaking with the owner, the veterinarian recommended a fecal float examination. I took a sample of feces from the cat, and when I took a look under the microscope I found numerous tapeworms eggs (Figure 2).
Figure 2. Tapeworm ova seen in a fecal examination microscope slide.
The cat owner was informed of the findings and was informed of the life cycle of the feline tapeworm (Figure 3). This life cycle involves an external parasite of the cat, a flea. Once attached to the cats intestine the worm begins to feed and reproduce. The veterinarian recommended Praziquantel (a drug used to expel flatworms from the host) and Revolution (a long term flea prevention to prevent the cat from being infected with this parasite in the future) for treatment of the infection.
I became intrigued by Cestoda (the class of parasitic flatworms commonly called tapeworms). There have been over 1000 described species of tapeworms and virtually all vertebrates can become parasitized by at least one species of tapeworm. Tapeworms are particularly interesting parasites because they display a variety of complicated life cycles with many intermediate hosts (also called transition hosts) to infect the definitive host (the host in which the parasite reaches complete maturity and can reproduce).
As I read more about tapeworms, I developed interest about the “crowding effect” in tapeworm infections. The “crowding effect” is when the number of worms in a host increases, the size of the individual worms decrease. In other words, a host with lots of tapeworms will have smaller worms than a host with few tapeworms. This can be caused by many reasons including competition between the worms and the role of the host’s immune system.
Currently, I am beginning a meta-analysis approach to research the “crowding effect” in tapeworm infections. Meta-analysis is a research method focused contrasting and combining results from different published studies in hopes to identify a significant pattern. I would like to find out if the “crowding effect” is seen in both cases where the host has tapeworms of the same species in the gut, and when different species of tapeworms reside in the host. Competition is expected to vary depending on whether the tapeworms are more or less related, and this should have an effect on the number and size of the worms. I hope to find out that the crowding effect is more prevalent in hosts that have many of the same species of tapeworms than different species. This research will lead to a better understanding of tapeworm infections in vertebrates and may even help us realize the value of the success of tapeworm treatment.