Parasites
by
Edward M. Craft
Parasites are harbored by all species of reptiles and as a result this section will contain several key points concerning them. Parasites are probably one of the most over looked aspects of the general health of captive reptiles. They are small organisms that live in their host and in some cases are actually beneficial to the host animal. If all parasites where to be harmful to their host causing their death than the parasites would eventually bring about an end to their own existence by eliminating the very hosts that they need to survive. This is only true of some species of parasites and in some cases the existence of parasites can cause serious illness and may even lead to death if left untreated for an extended period of time. For this reason it is important to understand what types of parasites are harmful to what species of reptiles and which parasites are needed by their host reptiles to aid in processes such as digestion. Simply random deworming may eliminate both harmful and beneficial parasites as well. It is very important to understand what parasites are beneficial and which are harmful as well as the method by which they are transmitted and the relationship they have to the host.
Parasites require a host. This is an animal that will harbor the parasite and provide it with nutrition, protection from the environment and a safe place to reproduce. The type of host that meets all three of these requirements is known as the DEFINITIVE HOST and is the primary host of the parasite. There are other types of hosts such as the DEAD END HOST that is a type of host that only provides the parasite with a food source.
Parasites like most living organisms go through a life cycle and may be simple or complex. If the parasite has a simple life cycle it may only require a definitive host all of its life, this is known as a DIRECT LIFE CYCLE. If a parasite has a complex life cycle it may require several hosts throughout this cycle and are necessary for reproduction. This is known as an INDIRECT LIFE CYCLE and requires an INTERMEDIATE HOST during the parasites life cycle.
These are the different types of hosts and as you can see there is a difference between them. It is vital that a parasite find a definitive host to reproduce, but it may survive and live out its life in a dead end host dying when the host dies without reproducing. It is also possible for a parasite to pass through an intermediate host temporarily until it is passed on to a definitive host where it will grow, reproduce and flourish.
After taking a look at the life cycles of parasites let us consider the methods of transmission. It is through an understanding of this portion of the life cycle that most concerns us when it comes to prevention. In parasites with a direct life cycle the ORAL-FECAL route is the most common method of transmission and occurs when the parasite is shed in the fecal matter or oral secretions of the host and is ingested in food or water by the new host. This may not seem to be a problem for the host because the parasite will eventually be shed to a new host, but this is not the case. Often times the same host is re-infected with the parasite and the parasite load within the animal continues to grow as the parasites reproduce within the host and the host continuously re-ingests more and more parasites.
Parasites with a complex life cycle will often reproduce in the host and shed eggs or larvae through nasal, oral or fecal secretions. The eggs or larvae or then ingested by an intermediate host, such as a mouse or rat, where they will continue to grow until the intermediate host is ingested by the definitive host where the process begins all over again. It is possible in the case of some parasites with a complex life cycle to end up in humans where they may survive with the human being a dead end host rather than a definitive host and is why proper sanitation is necessary when cleaning cages.
Captive reptiles are kept in a limited space without exposure to other animals and as a result parasites with a complex life cycle that require and intermediate host will not have access to that host, but instead will continue to re-infest the primary host over and over again. Practicing proper husbandry and cleaning by removing all fecal and waste materials will help to prevent the spread of parasites.
You may be asking yourself at this point why it is that if reptiles naturally harbor parasites in the wild why are they a problem in captivity. The answer relates to the fact that as stated earlier, if parasites killed their hosts they would eventually kill themselves. In the wild there is a greater number of reptiles spread over a greater area which means that wild reptiles would have a small and manageable parasite load compared to their captive counterparts which are confined to a much smaller area without the benefit of intermediate or other definitive hosts leading to greater parasite burdens within an individual captive reptile.
Heavy parasite burdens in captive reptiles present a threat to the immune system and combined with the added stress of captivity are enough to cause severe illness and in some cases death. These are factors that are not present in wild reptiles and as a result allow the parasite and wild host to live harmoniously in most cases.
Diagnosing the existence of parasites is vital in captive reptiles. More and more pet stores and breeders are having their reptiles screened for parasites prior to their sale, but it is important that owners do not rely on these screens as un-trained or inexperienced personnel often perform them. To properly screen for parasites an owner should collect a fresh fecal sample and place it in a plastic bad or container and place that bag or container in another plastic bag. This bag should be labeled with the date and time that the sample was collected and placed in the refrigerator until it may be taken to an experienced reptile veterinarian for examination. Placing the bag in a refrigerator that will not be used for human food storage is preferred for obvious reasons.
A fecal sample may be examined microscopically for the presence of adult parasites, larvae and eggs. It is best to have your veterinarian perform both a direct fecal smear and a fecal float.
Proper diagnosis of the species involved is vital to proper treatment. Random deworming is often performed by pet stores and breeders and is not the proper method for treating parasites. Not all antiparasitasides kill all species of parasites.
There are two primary types of parasites. Ectoparasites such as mites and ticks which are not much of a problem in aquatic reptiles, but can be a problem for snakes, lizards and terrestrial chelonians. Crocodilians do not seem to be effected by this type of parasite unless an open wound is involved. The primary type of parasite that effects aquatic chelonians and crocodilians are leeches. Crocodilians are also known to host parasites such as nematode worms that lay their eggs in the skin of the crocodilian, which are known as SKIN TRACKS or SQUIGGLES. These parasites are sometimes mistaken for integumentary sense organs found in the subfamily Crocodylinae and Gavialinae. These organs are located at the rear portion of the scales and are normal for crocodiles and gavials.
There are five primary species of ectoparasites, (See table 1), that effect reptiles. These parasites are most commonly found in wild caught, imported or newly acquired reptiles and are more of a nuisance than anything else. If left untreated they may present a major health risk to captive reptiles.
Table 1
Ectoparasites
Parasite/ Preferred Reptile Host/ Location
TICKS/ Snakes, Lizards, Chelonians/ Skin
MITES/ Snakes, Lizards, Semi Aquatic turtles/ Skin, Scales, Cloaca
CHIGGERS(Larva of Trombiculid mites)/Snakes, Lizards/ Skin folds, Joints
MYIASIS(Flies, mosquitoes, fleas and gnats)(Eggs are deposited)/ Snakes, Lizards, Semi Aquatic turtles/ Skin, Scales
LEECHES(Both salt & fresh water species)/ Aquatic turtles, Crocodilians/ Skin, Mouth
The second group of parasites that effect reptiles are Endoparasites. These are perhaps the group of parasites that pose the greatest health risk to captive reptiles. These parasites may effect the internal organs of the host and in a captive environment where an intermediate host is not present may multiply and re-infect the host causing very serious complications. Prevention and control of this group of parasites is vital in a captive environment and all possible methods for diagnosis, treatment and prevention should be practiced.
This group may be broken down into four sub-groups, (See table 2). These sub-groups consist of PROTOZOA, TREMATODES, CESTODES and NEMATODES. Of these for sub-groups it is the NEMATODES that are most often misdiagnosed as other illnesses altogether as a result of the similarity in symptoms that the create to other illnesses.
Members of the nematode family such as Pentastomiasis and Rhabditida are commonly found in the lung tissue of the host and present symptoms that often resemble those of a common respiratory infection. Symptoms of a Pentastomiasis or Rhabditida infestation are an oral and nasal discharge, open mouth breathing, lethargy and an increased respiratory rate. As a result many owners and breeders will treat their reptiles based solely on symptoms an if the treatment is unsuccessful than the owner assumes that it was a result of a respiratory illness, never knowing that it may have been a parasite infestation that was the true underlying cause of death. Through proper diagnostic testing the death of the reptile may have been prevented and a proper course of treatment may have been used to save the animal.
Since some parasites are difficult to detect through a fecal examination other diagnostic techniques may be required if symptoms of illness are present. Other techniques should include a radiograph and if respiratory signs are present than a tracheal wash should be performed to rule out the presence of pentastomiasis and rhabditida. These parasites are often commonly called tongue and lungworms for obvious reasons and do carry the potential for transmission to humans as a dead end host.
Table 2
Endoparasites
Parasite/ Prefered Reptile Host/ Location
PROTOZOA
AMOEBIASIS/ Snakes, Lizards/ Intestinal tract
COCCIDIOSIS/ Snakes, Lizards, Chelonians, Crocodilians/ Intestinal tract
CRYPTOSPORIDIOSIS/ Snakes, Lizards/ Intestinal tract
HAEMOGREGARINES/ Snakes, Lizards, Chelonians, Crocodilians/ Blood stream
PLASMODIUM & HAEMOPROTEUS/ Snakes, Lizards, Chelonians, Crocodilians/ Blood stream
TRYPANOSOMIASIS/ Snakes, Lizards, Chelonians, Crocodilians/ Blood stream
CILIATED PROTOZOA(Considered to be beneficial to some species)/ Lizards, Chelonians/ Digestive tract
FLAGELLATED PROTOZOA(Some species not harmful to crocodilians and to crocodilians and chelonians)/ Snakes, Lizards, Chelonians, Crocodilians/ Digestive tract
SARCOSPORIDIOSIS/ Aquatic Chelonians/ Gallbladder
TREMATODES
MONOGENEA(Difficult to diagnose)/ Chelonians/ Urinary bladder, Nose, Mouth, Esophagus
DIGENEA/ Crocodilians/ Digestive tract
ASPIDOGASTREA/ Chelonians/ Alimentary tract
SPIRORCHIDAE/ All, esp. Chelonians/ Circulatory system
STYPHLODORA/ Snakes/ Renal tubules, Cloaca, Ureters
CESTODES
PSEUDOPHYLLIDEA/ All, esp. Pythons/ Muscles, Sub-cutaneous tissue
PROTEOCEPHALIDEA/ Snakes, Varanid Lizards/ Small intestines
MESOCESTTOIDIDAE/ Snakes, Lizards/ Intestinal tract
ANOPLOCEPHALIDAE/ Lizards, Chelonians, Snakes/ Intestinal tract
NEMATOTAENAE/ Lizards/ Intestinal tract
DILEPIDIDAE/ Snakes, Lizards/ Liver
NEMATODES
ASCARIDS/ All/ Gastric mucosa
RHABDITIDA/ All, esp. Varanid Lizards/ Lungs
STRONGYLOIDS/ All/ Esophagus, Intestine
ACANTHOCEPALINS/ Chelonians/ Small Intestine
FILARIDS/ All/ Blood stream
PENTASTOMIASIS/ All, esp. Varanid Lizards/ Lungs, Esophagus
OXYURIDS/ Lizards, Chelonians, Some snakes/ Lower intestine
CAPILLARIA & EUSTRONGYLIDES/ Snakes, Lizards, Chelonians/ Liver, Bile Duct
Proper treatment of parasites involves knowing which parasite is involved and the life cycle of that parasite. Without breaking the life cycle of the parasite re-infestation will most likely occur and all the deworming in the world will not help to eliminate the problem. Identifying the parasite involved is just as important and is best left up to trained professionals who are experienced with identifying parasites that prefer a reptile host.
Since parasites range in their relationship to the host from beneficial to a serious threat to the life of the host animal, identification is the key to proper deworming. Fecal examinations should be performed by an experienced reptile veterinarian on an annual basis to assure that your reptile remains parasite free, particularly in species that eat small mammals.
