Introduction
There are over 7200 species of reptiles divided into the orders Squamata (snakes and lizards), chelonians, Crocodilia, and sphenodontia (tuataras). In recent years, many advances have been made in infectious diseases identification, testing and treatment. Reptile ownership is increasing and as it does the demand for medical care has grown. Likewise, many practitioners are also asked to care for wildlife reptiles that present to their practice. A good understanding of infectious diseases clinical signs, basic pathogenesis, treatment options and diagnostics will help facilitate caring for reptile patients.
1. Tortoise Virus 5 and Turtle Virus 32,3
a. Both viruses are ranaviruses in the iridovirus family.
b. The primary lesions are necrotizing stomatitis, esophagitis, splenitis, and fibrinoid vaculitis.
c. Inclusions can be rare to see but when noted are basophilic intracytoplasmic.
d. Clinical signs are caseous oral plaques, nasal discharge, palpebral and cervical edema.
e. The reservoir for chelonian ranaviruses is amphibians especially Xenopus species like the African clawed frog via ingestion of an amphibian, waterborne infection, or via systemic infection and then vector borne transmission.
f. PCR testing is recommended since the proteins for Ranaviruses are conserved across species. Virus isolation and electron microscopy can also be done.
2. Inclusion Body Disease1,7
a. Inclusion Body Disease is a retrovirus.
b. The species affected is pythons and boas primarily but it has been seen in some non-boid snakes as well.
c. The Primary lesion is gastrointestinal but the disease can have respiratory and neurologic signs as well.
d. Clinical signs:
i. In young boas the disease is fatal with acute onset of paralysis.
ii. In adult boa snakes it is a more chronic disease with regurgitation and chronic pneumonia with central nervous systems signs late in the disease.
iii. In pythons the disease is more rapid and progresses to fatal central nervous system signs quicker and multisystemic disease is very common with pneumonia and infectious stomatitis.
e. The transmission is through direct contact, venereal and arthropod means via the snake mite Ophionyssus natricis.
f. The best testing method is PCR.
3. Adenovisus7
a. The species affected is lizards especially bearded dragons and snakes especially boids, colubrids and vipers.
b. The clinical signs are weight loss, regurgitation, diarrhea, central nervous system signs and hepatitis.
c. The primary lesion is hepatic necrosis and basophilic intranuclear inclusion bodies.
d. The gross signs are subcutaneous, coelomic and intestinal hemorrhages.
e. Transmission is predominantly fecal-oral
f. The testing methods include viral isolation (VI), cytology, electron microscopy (EM).
4. Paramyxovirus7
a. The species affected is vipers but it can also be seen in boids, pythonidae, colubrids and elaphids.
b. The primary lesion is pneumonia but neurologic signs and regurgitation with high mortality is also seen.
c. Clinical signs are nasal discharge, open mouthed breathing, accumulation of caseous debris in the oral cavity and harsh respiratory sounds as well as head tremors, writhing, star gazing, unresponsive episodes and regurgitation.
d. Testing is best done with either PCR, VI, EM of feces or respiratory secretions via tracheal wash, and hemagglutination inhibition (HI) test for paired plasma titers.
e. Transmission occurs through ingestions and inhalation.
f. Clinical signs:
i. In the acute/peracute form, the animal is found dead before antibody response or clinical signs can appear.
ii. The chronic poor doer stage can present with anorexia, regurgitation, respiratory illness and central nervous system signs with a high titer but and the animals usually die.
iii. Clinically healthy animals that are asymptomatic for up to 10 months and then eventually become poor doers can also be seen. Keep in mind a high titer may indicate a carrier state and not necessarily immunity.
5. Chelonid Herpesvirus6,7
a. The species affected is chelonians.
b. The primary lesions and clinical signs are mild conjunctivitis, nasal discharge, glossitis, enteritis, pneumonia, meningoencephalitis and necrotizing stomatitis with pharyngitis and plaques in the oral cavity.
c. On histology, intranuclear inclusion bodies are often seen.
d. Testing can be done with serology, PCR, EM and VI.
e. Transmission occurs through direct contact and possible vertical transmission.
f. The Reservoir species are the Mediterranean and red footed tortoises.
6. West Nile Virus (WNV)4,5,7
a. WNV is a Flavivirus.
b. The reptile species affected was crocodilians.
c. The primary lesion is heterophilic lymphoplasmacytic meningoencephalitis.
d. Secondary lesion that are sometimes seen are lymphohistiocytic proliferative syndrome of the superficial dermis, necrotizing heterophilic hepatitis and splenitis, myocardial degeneration and mild pneumonia.
e. Clinical signs are swimming in circles, head tilt, muscle tremors, weakness, lethargy and anorexia.
f. The vector: is Culex species of mosquitoes.
g. Transmission is through arthropods and horizontal transmission.
h. Testing is via ELISA, HI, and PCR especially RT-PCR
7. Cryptosporidium serpentis and saurophilus7,8
a. The species affected with serpentis is snakes and saurophilus in lizards especially geckos
b. Primary lesion: Hypertrophic gastritis in snakes and intestinal hypertrophy in geckos
c. Clinical Signs:
i. Subclinical with intermittent fecal shedding is usually seen in snakes more than other reptile groups.
ii. Clinical disease included weight loss with persistent or post-prandial regurgitation 3-4 days after ingestion affecting all age ranges and is not self-limiting.
d. Testing is through fecal cytology from cloacal or gastric wash, and via gastric biopsy.
e. The transmission is fecal-oral
8. Entamoeba invadens7
a. The species affected is snakes and lizards with chelonians and crocodilians being mainly carriers and resistant to disease.
b. The primary lesion site is the colon.
c. Clinical signs are GI perforation and abscesses in liver, kidney and central nervous system signs
d. Testing is through fecal float for cysts or trophozoites but trophozoites in the fecal sample deteriorate quickly.
e. Transmission occurs via fecal oral, direct contact, fomites.
9. Mycoplasma agassizii6,7
a. The species affected are chelonians especially the desert and gopher tortoise.
b. The lesions and clinical signs are rhinitis with nasal and ocular discharge, conjunctivitis, palpebral edema and death.
c. Testing: is with ELISA for antibodies, culture, PCR, or histopathology.
d. Transmission occurs via direct contact especially when there is nasal discharge present.
e. Other mycoplasmas: M. iguanae affecting iguanas, M. alligatoris affecting the American alligator and broad nosed caiman, M. crocodyli affecting primarily Nile crocodiles
References
1. Carlisle-Nowak, M., N. Sullivan, M. Carrigan, C. Knight, C. Ryan and E. Jacobson. 1998. Inclusion body disease in two captive Australian pythons (Morelia spilota variegata and Morelia spilota spilota). Aust. Vet. J. 76 (2): 98-100.
2. De Voe, R., K. Geissler, S. Elmore, D. Rotstein, G. Lewbart, and J. Guy. 2004. Ranavirus-associated morbidity and mortality in a group of captive eastern box turtles (Terrapene carolina carolina). JZWM 35(4): 534-543.
3. Johnson, A., A. Pessier, J. Wellehan, A. Childress, T. Norton, N. Stedman, D. Bloom, W. Belzer, V. Titus, R. Wagner, J. Brooks, J. Spratt and E. Jacobson. 2008. Ranavirus infection of free-ranging and captive box turtles and tortoises in the United States. J. Wildl. Dis. 44(4): 851-853.
4. Nevarez. J., M. Mitchell, D. Kim, R. Poston, and H. Lampinen. 2005. West Nile Virus in alligator (Alligator mississippiensis) ranches from Louisiana. J. Herp. Med. Surg. 5: 4-9.
5. Nevarez, J., M. Mitchell, T. Morgan, A. Roy, and A. Johnson. 2008. Association of West Nile Virus with lymphohistiocytic proliferative cutaneous lesions in American alligators (Alligator mississippiensis) detected by RT-PCR. J. Zoo. Wildl. Med. 39(4): 562-566.
6. Origgi, F., and E. Jacobson. 2000. Disease of the respiratory tract of chelonians. Vet. Clin. North Am. Exot. Anim. Pract. 3(2): 537-549
7. Ritchie, B. 2006. Viral diseases. In: Mader, D.R. (ed.). Reptile Medicine and Surgery. W.B. Saunders Co., Philadelphia, Pennsylvania. Pp. 391-417.
8. Terrell, S., E. Uhl, and R. Funk. Proliferative enteritis in leopard geckos (Eublepharis macularius) associated with cryptosporidium sp. infection. J. Zoo. Med. Surg. 34(1): 69-75.