Common parasitic diseases of reptiles and amphibians (Proceedings)

In this presentation we will discuss the various groupings of parasites seen infesting reptiles & amphibians, how to identify them and thoughts on proper treatment to rid the hosts of these parasites.

It is believed that all reptiles and amphibians living in the wild harbor parasites. The delicate balance between parasite and host in the wild tends to vary dramatically from the relationship between parasite and host in captivity. In the wild, where an animal is not confined within a small space, the environmental concentration of parasites is not high. As a result, the parasite burden to any given host is usually low. However, in captivity, especially in poor sanitary conditions, the concentration of parasites may be much higher, and therefore more dangerous. Couple this higher parasite concentration with the stress from poor husbandry (i.e. Improper: temperature, nutrition, light exposure, overcrowding, etc.) and these stressed captive animals with heavy parasite loads are more likely to succumb to the parasite infestation.

Parasites affect their hosts in many different ways. The parasites can be external (e.g. ticks and mites) or internal (e.g. gastro-intestinal worms). Parasites appear to have an affect on all aspects of captive rearing. In general parasitized reptiles and amphibians have a shorter life span, tend to be more susceptible to disease, and have a generally unthrifty appearance. Also, studies have demonstrated that heavily parasitized reptiles have poor to no ability to reproduce. And, of those that do succeed in producing offspring, the offspring may die at a young age, can be stunted, or have very slow growth rates.

So it is for these reasons that it is strongly recommended to accurately diagnose and treat for all observed parasites in captive reptiles and amphibians. Concerning proper treatment of reptiles and amphibians, each animal has to be treated on a case by case basis. In the literature and formularies there are several different doses as well as different treatment schedules listed – it behooves the veterinarian to evaluate each dose and regimen individually for each particular animal.

Enteric Parasites

Protozoa

The numbers and genera of protozoa present in an amphibian or reptile are very often influenced by the individual animal differences in the physiological parameters that effect the intestinal tract. Such differences, i.e. hydration status, pH, and the passage of digesta can have a profound effect on the make up of the enteric protozoal community. Other factors can include natural antagonism between the different species of parasite and predation. Protozoa can also effect the bacterial flora due to substrate competition and predation and thus can have secondary effects on the homeostasis of the intestinal tract.

Flagellates

Thus far at least 6 genera of flagellates have been identified, and these have probably been transmitted by infective cysts or by copulation. The organism most likely to cause problems in captivity is Hexamita, which has been known to affect the urinary bladder and kidneys of aquatic turtles (renal hexamitosis) and is often a fatal infection. Chilomastixis frequently found in the intestine of salamanders, frogs and toads. Tritrichomonas and Trichomonas, typically identifies by their well developed undulating membrane, are widely distributed among amphibians and reptiles. Giardia are also frequently seen in amphibians and reptiles. Retortamonad and diplomonad flagellates have also been reported in poison dart frogs.

Ciliates

Balantidium species are common in herbivorous turtles and lizards. It is thought that unless this ciliate is present in large numbers, that it is unlikely to be causing any pathogenic effect. But again, considering the other possible stresses placed on the animals in captivity – I usually recommend treating for these parasites. Nyctotherus, another very large ciliate, can be found in turtles and the green iguana (Iguana, iguana, iguana). The cyst of this "commensal" can easily be mistaken for a trematode egg. Nyctotheroides has been observed in anurans.

Opalinids

These organisms resemble flagellates and ciliates. However, opalinids lack a cell mouth and have only one type of nuclei. Zelleriella were observed in dendrobatid frogs.

Amoeba

In reptiles and amphibians, clinical signs of anorexia, weight loss, blood or mucus in the feces, vomiting, green discoloration to the urates, or midbody to caudal swellings of the body may be suggestive of infection with Entamoeba invadans. This is a highly pathogenic parasite in lizards and snakes. The trophozoites may be observed in a direct smear of the fecal material. Amoeba may be commensal symbionts in turtles and crocodilians, frequently making them responsible for infection of exposed snakes and lizards. Several other species of pathogenic amoeba exist, of which Acanthamoeba has been implicated in fatal infections. Star gazing is thought to be a sign of central nervous system involvement with this organism.

Treatment for amoebae, flagellates and ciliates is typically with metronidazole (100 mg/kg PO repeated in 2 weeks / or 50 mg/kg PO q 24h x 3-5 days +/- repeat PRN) [As is the case with all medications used in reptiles and amphibians, each animal has to be treated on a case by case basis – for all medications, in the literature there are several different doses as well as treatment schedules listed – it behooves the veterinarian to evaluate each dose and regimen individually for each particular animal]

Coccidia

Isospora and Eimeria are the coccidia most recognized in the fecal specimens of infected amphibians and reptiles. Listlessness, anorexia, regurgitation and intestinal hemorrhage and at times intussusception are the typical signs of intestinal or gall bladder infection with coccidia. Isospora have two sporozoites and have not been reported in turtles. Eimeria have four sporozoites and it is considered the primary coccidian of reptiles. Oocysts are ingested from contaminated soil or feces, and I am concerned with the possible vector transmission of insects that have ingested contaminated matter. Sarcocystis and Toxoplasma are occasionally found in reptiles. Typically it is believed that the affected reptiles if the intermediate host, though reports exist for snakes and lizards serving as the definitive hosts.

Effective treatment for coccidia resulting in complete cure of the infestation can be difficult. I typcally us sulfamethoxine and sulfamethzine at 75 mg/kg once daily for 7 days. Proper husbandry and hydration of the patient as well as sanitation is very important to try and achieve best success with treatment.

Cryptosporidium has frequently been seen in Biods. Typical presenting complaints by the owner is of regurgitation, lethargy, depression and frequently a midbody swelling may be palpated in advanced cases. The organism causes a proliferative gastritis for which there is presently no know cure or effective treatment. The transmission is via the ingestion of sporulated oocysts, infected mice, snakes, lizards or other prey items. A definitive diagnosis can be made on the basis of a direct smear or an acid fast stain preparation of: the feces, the slime coat from a regurgitated meal, or an aspirate/stomach wash that reveals multiple round organisms, 2 to 5 microns in diameter, staining bright red. Sometimes the organisms will not retain the red dye but will leave a "ghost image" against the counter stain. Careful identification must be made in male snakes as to not mistake tailless spermatozoa, which will also take up the red stain, for coccidian oocysts. Oocysts may be shed intermittently and therefore repeated fecal evaluations of a biopsy may be required to arrive at the definitive diagnosis. Infected animals should be completely isolated from the collection and due to the potential for zoonotic threat, and due to the fact that effective treatment for cryptosporidia is typically unsuccessful at the present time, it is often recommended that they be humanely euthanized and destroyed. An option to attempt treatment as reported by Dr. Elliot Jacobson is SMZ-TMP at 30-60 mg/kg PO SID for 60 days, or Paromomycin (300-800 mg/kg PO q 24-48h X 7-14 days/or/PRN).

Helminths

Nematodes

The presence of thin-walled embryonated eggs or rhabditiform larvae in a fecal sample are indicative of Strongyloides or Rhabdias infestation. Rhabdias inhabits the hosts lungs and may cause respiratory distress. Strongyloides can produce diarrhea and respiratory distress as infective larvae migrate through the host's lungs. Both parasites may cause anorexia, weight loss and debilitation. The life cycle is direct and the parasite can be transmitted by ingestion of eggs, larvae, or possibly by direct skin penetration. These parasites can exist as a free-living form, making proper and complete cage sanitation a necessity. Oxyurid eggs are frequently encountered during fecal examinations of lizards and chelonians. In snakes, care must be taken not to mistake rodent pinworm eggs for those parasitic for reptiles. Pinworms are considered by many as non-pathogenic, though I typically treat to avoid any possible problems associated with their presence. Oxyurids have a direct life cycle and can exist insignificant numbers within the colon, especially of tortoises, putting them at possible risk for impaction. Anorexia may occur in animals coming out of hibernation and may be attributed to heavy oxyurid infestation. Two genera of hookworms, Kalicephalus and Oswaldocruzia, occur in reptiles throughout the world, and usually appear similar in appearance. Fecal examination will demonstrate the presence of typical "strongyle type" eggs. Transmission is by ingestion of ova, infective larvae, or possibly by skin penetration. The drinking of contaminated water is another means of oral transmission. Infestations may cause lethargy, anorexia, general debilitation, anemia, ulceration, intestinal obstruction and peritonitis. Capillaria is the only known trichurid genera affecting reptiles. These nematodes primarily infect the intestine but have been found in other organs, such as the liver and gonads. They have a direct life cycle. Diagnosis is based on the presence of eggs with opercula at either end. Ascarid eggs are recognized by their thick shells Adult worms may be found embedded in the stomach, esophagus, or small intestine where their effect may range from no apparent signs of illness too anorexia and regurgitation. Diarrhea and purulent pneumonia may also be attributable to heavy worm infestations. The most likely source for transmission is through the ingestion of intermediate hosts, such as amphibians and rodents. Spirurids are parasites of the mouth and gastro-intestinal system. Reptiles may act as either intermediate or definitive hosts. For terrestrial reptiles and amphibians, ants are a common source for infection. In aquatic animals, Copepods are a common souce for transmission. Diagnosis is by detection of the characteristic eggs. On microscopic exam, the larva are curled within giving the egg the appearance of containing a paper clip. Adult worms are easily removed from the mouth. Filariae can be found within lymph vessels, the eye, subcutis or within the coelomic cavity. The microfilaria produced by the adults may circulate in the blood or may be found in the skin, where they may cause dermal tumors. Pathology due to filarae is rare.

Treatment of nematode infestation can be accomplished using a variety of anthelmentics. For example: thiabendazole (50-100 mg/kg PO), levamisole (5-10 mg/kg PO), fenbendazole (50-100 mg/kg PO) Piperazine (40-60 mg/kg PO) ivermectin (o.2 mg/kg PO, IM or SC)[Do Not Use Ivermectin In Chelonians, Indigo Snakes & Skinks] Milbemycin (o.5 – 1.o mg/kg PO) can also be used in reptiles and has been injected in several species of turtles with no ill effects. All treatments are repeated in two weeks, followed by a fecal examination 14 days after the second dose. If positive for parasites, a third dose is given, and the cycle continued until the parasites are cleared from the animal.

Cestodes

The tapeworms that affect reptiles are hermaphroditic and non-host specific. Tranmission is by ingestion of an intermediate host. Diagnosis of an intestine dwelling cestode is by detection of proglottids or eggs in the stool. Plerocercoids of Diphyllobothrium are frequently found in tadpoles feeding on crustaceans. Niclosamide (150-300 mg/kg PO), bunamidine HCl (50 mg/kg PO), and praziquantel (7-8 mg/kg IM,PO,SC), each repeated in two weeks are all reported to be effective in treating adult tapeworms.

Trematodes

Operculated eggs in the fecal sample or oral mucosa are diagnostic for trematodes. Some monogenea are external or urinary bladder parasites of frogs, tadpoles and newts. Digenean trematodes often form metacercariae in the skin, eye or various organs. The renifer group of digenetic flukes are common in the mouth, pharynx, esophagus, trachea, and lung of indigo snakes. This fluke requires an amphibian intermediate host therefore elimination of this food source or freezing/preparing the prey item to kill potential parasites is required to prevent reinfestation. The infected animals are often presented for anorexia or profuse salivation, due to the large number of organisms present in the oral cavity. Praziquantel (7-8 mg/kg IM,PO,SC) or fenbendazole (100 mg/kg PO) repeated in two weeks will control this and other metazoans.

Acanthocephalans

The thorny-headed worms or acanthocephalans are common in aquatic trutles, frogs and toads. They may be found in the stomack or intestine. Clinical signs may include blood or mucus in the stools, anemia, and weight loss. The eggs are typically dark, thick-shelled and tapered at the ends, with fecal materials frequently adhering to the shell. Levamisole at 5-10 mg/kg PO,SC,ICe repeated in two weeks has been used successfully for treatment.

Pentastomes

Pentastomids are considered to be a degenerative crustracean that parasitizes the lung and airsac distal to the lung. Larvae and nymphs may be found in the stomach wall. Transmission occurs by the ingestion of an intermediate mammalian host. Symptoms may include lethargy, anorexia, dyspnea, and blood tinged saliva. Affected animals frequently harbor these parasites with no ill effects. Diagnosis is based on observations of the characteristic eggs which contain a promary larva, which is oval, tailed, and has four stumpy legs each bearing one or two retractable pincer claws. Humans can be an acidental host, so care must be taken when handling infected animals and their feces. There is no known completely effective treatment, though levamisole (5 mg/kg PO, SC, ICe) or one of the avermectins (Ivermectin or Milbemycin) may be effective.

Hemoparasites

At this time, only the most common blood parasites will be discussed, as the number of described species is extensive and the literature is often not helpful in determining the pathogenicity of certain species. Hemoparasites are found within the cells or free in the plasma. Their development may involve other organ systems. Often, with blood parasites, there is little or no clinical disease. Clinical signs that may develop with hemoparasites include anemia, thrombocytopenia or purpura. There is little or no data on the efficacy, but hemoprotozoa are often treated with tetracycline (10 mg/kg PO q24h) and/or chloroquine phosphate-primaquine phosphate (125 mg/kg PO q 48h X 3 treatments) or Quinacrine (19-100 mg/kg PO q48h X 2-3 wk).

Hemogregarines

A single schizont typically attacks a RBC, where replication occurs intracytoplasmically. Hemogregarines are the dominant and characteristic hemoparasites of snakes but affect all classes of reptiles including the Tuatara and sea snakes. Hemogregarina is found in aquatic reptiles and relies on leeches for sexual reproduction. Hepatozoa is found in terrestrial arthropods or leeches. Typically there is little pathology.

Hemoproteus

These are also found within the erythrocyte cytoplasm and vary from one to several per cell. Turtles and lizards are the usual hosts. Typically there is little pathology.

Leishmania

With this hemoparasite, only the pro- and amastigote stages are observed. Promastigotes are found in the blood, amastigotes are intracellular. Transmission is probably by the sandfly. This is a benign infection, with lizards as the hosts.

Plasmodium

There are 68 species known that have been identified in turtles, lizards and snakes. Depending on the species, different stages of the organism may be found within the cytoplasm of the RBC's, mononuclear leukocytes or endothelial cells of visceral organs. Some species may cause anemia or thrombocytopenia. An insect vector is required for transmission.

Lankesterella

This protozoan hemoparasite may be transmitted by leeches. They penetrate and destroy RBC's potentially resulting in anemia.

Trypanosomes

These affect crocodilians, turtles, lizards, snakes, frogs and newts. Biting flies and leeches are responsible for transmission. Effected animals may demonstrate listlessness, refuse food, and potentially die due to heavy parasitism, however pathology is usually rare.

Microfilaria

The presence of microfilaria in the blood suggests the presence of a pair of adults in the animal, i.e. the eye, subcutis or coelomic cavity. Typically pathology is rare with the exception being the presence of adults in the eye.

Flukes

Spirorchis is found in the blood of semiaquatic turtles.

Pirhemocyton

This organism has been included under hemoparasites because when it was first described, it was believed to be a protozoal of erythrocytes. Presently it is thought to be an iridovirus. It is responsible for RBC destruction and anemia. If the affected animal also has a concomitant infection with Plasmodium, death often results.

Ectoparasites

Acariasis

An infestation with ticks and mites, can be both a nuisance and a costly problems for any animal collection. Both hard and soft shelled ticks attack reptiles and are usually seen on newly imported snakes. One must pay careful attention to the labial pits in boids , as this is a common site for infestation. The ticks can cause anemia and are responsible for the transmission of blood parasites or allowing bacteria to invade the wounds they produce. Treatment is their identification and removal. Ophionyssus mites are the most common and most pathogenic of the mites that attack reptiles. With out proper treatment, mite numbers can increase at such a rate, that even moderately sized animals can be exsanguinated. Mites can also transmit blood parasites and are also believed to transmit the virus responsible for boid encephalitis. Treatment is with ivermectin (Not in Chelonians) or milbemycin, warm water soaks, Fipronil [o.25%] {Beware of Reaction to alcohol carrier/use with caution/extra-label use – need further evaluation}(spray/wipe over q 7-10d), DDVP fly strips (i.e. Shell No Pest Strips or Vapona, are hard to find), or the careful application of pyrethroid {Permethran} [safe than Pyrethrins] insecticide, or Carbaryl powder {5%}. Silica gel may also be used as it dessiccates the mite by scratching the cuticle of the mite. However it can also dessicate small reptiles so close monitoring is required. Most reptile breeders have their own combination, i.e. olive oil + garlic + etc... and depending on the number of mites being treated these topical concoctions may be effected for treating the mites on the animals, but will not help with the treatment of the environment. One must always properly treat the cage, cage furniture, feed dishes, etc... if complete eradication of the mite infestation is to be achieved.

Myiasis

Turtles are particularly prone to infestation by fly larvae. While there are several species of the true bot fly, most cases of myiasis are by opportunistic species which exploit pre-existing wounds. Proper treatment consists of removing the maggots by flushing with dilute chlorhexadine solution and treating the wound both topically and often treating the animal systemically with appropriate antibiotic therapy. The toad fly, Bufolucilia, invades the nasal oriface of toads, and infestation is usually fatal.

Leeches

These are commonly found in certain reptiles, such as aquatic turtles as well as in amphibians. The dorsal lymph sac, body wall or body cavity may be invaded in certain species of frogs. Surgical removal is the only treatment method. Leeches have also been associated with cutaneous fibroepitheliamas in green sea turtles.

In conclusion, parasites whether internal or external are a real threat to captive amphibians and reptiles. Whether your client's animals are pets or commercial breeders, an effective parasite prevention/treatment program is essential. Parasitized amphibians and reptiles often have poor growth rates, are unthrifty, commonly have reproductive problems, and are in general more susceptible to disease than those same animals not infested with parasites. Since complete avoidance of parasites is difficult, especially in those animals that eat live food, I recommend at least yearly evaluations for external and internal parasites and appropriate treatment as indicated.

References and Suggested Reading

Mader, D.R. (1996). Reptile Medicine and Surgery. Saunders Co., Phil., PA. p. 185 – 203, 341, 379-381.

Frye, F.L. 1991. Biomedical and Surgical Aspects of Captive Reptile Husbandry, 2nd edition, vol. 1. Krieger Publishing Co., Malabar, FL.

Bodri, M.S., (1994) Common Parasitic Diseases of Reptiles and Amphibians. Proc. 1st ARAV Conference, Pittburgh, PA. p. 11-17.

Klingenberg, R.J. (2000) Reptile Parasites. Proc. 2000 ARAV Conference, Reno NV. p. 193-194.

Cooper, J.E. (2001) Host:Parasite relations in reptiles and Amphibians. Proc. 2001 ARAV Conference, Orlando, Fl. p. 249-250.

Bruederle, J.A. (1998). CVMA Exotics Formulary. Chicago, IL. p. 16 - 29.

Carpenter, J.W., Mashima, T.Y. and Rupiper, D.J., 2001. Exotic Animal Formulary, 2nd edition.W.B. Saunders Company. Philadelphia, PA.