Infectious diseases in reptiles: an overview

Our knowledge of infectious agents found in reptiles has grown considerably in recent years. At the same time, we know that the relationship between infection and disease in reptiles depends on many factors. These include pathogen-specific (e.g. strain-specific characteristics, virulence factors) and host-specific factors (e.g. species, age, sex), but also environmental conditions (e.g. temperature, hygiene, season) and co-infections with other pathogens. Many infectious agents can also persist in reptiles, which is why quarantine is of particular importance in this animal group. The diagnosis of infections in reptiles has also made great progress in recent years. On the following pages you will find an overview of selected infectious agents that occur in turtles, snakes and lizards. The main focus is on microbiological pathogens (viruses, bacteria, fungi). If you are not sure which examination or which type of sample is preferable for the diagnosis of a certain disease, we will be happy to advise you.

Selected infectious agents, classified according to the organ systems most frequently affected:

Tortoises and turtles

Skin: Herpes-, rana-, papillomaviruses, various bacteria, various fungi (USA: Emydomyces testavorans); Respiratory tract: Herpes-, picorna-, adeno-, rana-, paramyxoviruses (a.k.a. ferlaviruses), mycoplasma, chlamydia, other bacteria, fungi, intranuclear coccidia (TINC); Gastrointestinal tract: Herpes-, adeno-, rana-, reoviruses, various bacteria, fungi, intranuclear coccidia (TINC), cryptosporidia, various other parasites

Snakes

Skin: arena viruses, papilloma viruses, various bacteria, ophidiomyces, fungi, intranuclear coccidia (TINC) Bacteria, Ophidiomyces ophidiicola, other fungi; respiratory tract: Nido-, Arena-, Adeno- Reo-, Paramyxo- or

Skin: Arena-, papillomaviruses, various bacteria, Ophidiomyces ophidiicola, other fungi; Respiratory tract: Nido-, arena-, adeno-, reo-, paramyxoviruses (a.k.a. ferlaviruses), sunshinevirus, mycoplasma, chlamydia, other bacteria, fungi, parasites; Gastrointestinal tract: Adeno-, arena-, herpes-, rana-, reoviruses, various bacteria, fungi, cryptosporidia, other parasites; CNS: Arena-, paramyxoviruses (a.k.a. ferlaviruses), sunshinevirus, Entamoeba invadens

Lizards

Skin: Rana-, irido-, herpes-, reo-, papilloma-, poxviruses, Devriesea agamarum, other bacteria, Nannizziopsis spp., other fungi; Respiratory tract: Paramyxoviruses (a.k.a. ferlaviruses), adeno-, reoviruses, chlamdia, other bacteria and fungi; Gastrointestinal tract: Adeno-, herpes-, irido-, reoviruses, various bacteria, fungi, cryptosporidia, other parasites; CNS: Adenoviruses

 

Table 1: Select infectious agents found in tortoises and turtles and their laboratory diagnosis

	Infectious agent	Affected species	Affected tissues and clinical signs	Samples for diagnosis*	Methods
Viruses	Adenoviruses	Tort and turt	From inapparent carriers to systemic disease and sudden death	Cloacal swabs, intestine, liver, other affected tissues	PCR
	Herpesviruses	Various	Mostly upper respiratory and GI tract, skin, in some cases inapparent infection	Oral swab, cloacal swab, skin, tissues (tongue, liver, brain, intestine, others)	PCR Sero: VN in tort
	Paramyxoviruses (ferlaviruses)	Esp. tort	Mostly pneumonia	Tracheal wash, oral and cloacal swabs, lung, other tissues	PCR
	Picornavirus (virus „X“)	tort	Softening of the carapace in juveniles, renal disease, rhinitis, in some cases inapparent infection	Oral swabs, cloacal swabs, various tissues	PCR, VI Sero: VN
	Ranaviruses	Tort and turt	Upper respiratory and GI tract, liver, blood vessels	Oral and cloacal swabs often not sensitive, blood can be tested, tissue samples best for virus detection	PCR, VI
	Reoviruses	Esp. tort	Respiratory tract, possibly also GIT	Oral and cloacal swabs, tissues	PCR, VI
Bacteria + fungi	Bacteria (aerob and anaerob)	All	Many facultative pathogens, can affect various tissues	Samples from lesions. Interpretation in conjunction with clinical signs	Culture
	Chlamydia	Esp. tort	Granulomas, rhinitis, pneumonia, myocarditis, hepatitis	Nasal washes, oral and cloacal swabs, affected tissues	PCR
	Mycobacteria	All	Esp. granulomas	Material from lesions	Histo, ZN
	Mycoplasma	Tort and turt	URTD	Oral swabs, nasal washes	PCR
	Fungi and yeasts	All	Many facultative pathogens, can affect various tissues	Samples from lesions. Interpretation in conjunction with clinical signs	Culture
Parasites	Cryptosporidia	Esp. tort	Depending on the parasite species, the stomach or the intestine may be affected	Faeces, gastric or intestinal mucosa, possibly gastric lavage, cloacal swabs	PCR
	Intranuclear coccidia (TINC)	Tort and turt	From inapparent carriers to systemic disease and sudden death	Cloacal swabs, oral swabs, faeces, tissues	PCR
	Parasites (others)	All	Esp. GIT, from inapparent carriers to severe infestations and death	Esp. faeces	N, flot

*The ideal sample depends on the stage of infection, type of pathogen, and host species and should be chosen based on the clinical question. Flot = flotation; GIT = gastrointestinal tract; Histo = histology; N = native; Sero = serology (antibody detection); tort = tortoise; turt = turtle; URTD = upper respiratory tract disease; VI = virus isolation in cell culture; VN = virus neutralisation test; ZN = Ziehl-Neelson stain

Table 2: Select infectious agents found in snakes and their laboratory diagnosis

	Infectious agent	Affected species	Affected tissues and clinical signs	Samples for diagnosis*	Methods
Viruses	Adenoviruses	All	Esp. GIT and liver	Cloacal swabs, faeces, intestine, liver	PCR, VI
	Arenaviruses	Boas and pythons	Inclusion body disease (IBD)	Oesophageal swabs, blood, tissues (esp. brain, liver, kidney, lymph., pancreas)	PCR, cyto, histo
	Herpesviruses	Various	Liver, kidney, oral mucosa, venom glands	Oral swabs, tissues	PCR
	Nidoviruses	Esp. pythons	Lung, upper respiratory tract, other systems, in some cases inapparent infection	Oral swabs, cloacal swabs, tissues	PCR
	Paramyxoviruses (ferlaviruses)	Various, esp. vipers, colubrids	Esp. respiratory tract	Tracheal wash, oral and cloacal swabs	PCR Sero: HI
	Ranaviruses	Various	Esp. liver, oral cavity	Oral and cloacal swabs often not sensitive, tissue samples best for testing	PCR, VI
	Reoviruses	Various	Respiratory tract, GIT, CNS	Oral and cloacal swabs, tissues	PCR, VI
	Sunshinevirus	Pythons	CNS, respiratory tract	Oral and cloacal swabs, tissues (esp. brain)	PCR
Bacteria	Bacteria (aerob and anaerob)	All	Many facultative pathogens, can affect various tissues	Samples from lesions. Interpretation in conjunction with clinical signs	Culture
	Chlamydia	Various	Granulomas, pneumonia, myocarditis, hepatitis, other tissues can also be affected	Oral and cloacal swabs, affected tissues	PCR
	Mycobacteria	All	Esp. granulomas	Material from lesions	Histo, ZN
	Mycoplasma	Esp. pythons	Upper respiratory tract	Oral swabs	PCR
Fungi	Ophidiomyces ophidiicola	Various	Skin	Skin (swabs, biopsies, exuviae)	PCR
	Fungi and yeasts	All	Many facultative pathogens, can affect various tissues	Samples from lesions. Interpretation in conjunction with clinical signs	Culture
Parasites	Cryptosporidia	Various	Stomach most often affected	Gastric lavage, regurgitated material, gastric mucosa	PCR, ZN, IFAT
	Parasites (others)	All	Esp. GIT, inapparent carriers to severe infestations and death	Esp. faeces	N, flot

*The ideal sample depends on the stage of infection, type of pathogen, and host species and should be chosen based on the clinical question. CNS = central nervous system; cyto = cytology; flot = flotation; GIT = gastrointestinal tract; HI = haemagglutination inhibition; histo = histology; IFAT = immunofluorescence antibody test; lymph. = lymphatic tissue; N = native; sero = serology (antibody detection); VI = virus isolation in cell culture; VN = virus neutralisation test; ZN = Ziehl-Neelson stain

Table 3: Select infectious agents found in lizards and their laboratory diagnosis

	Infectious agent	Affected species	Affected tissues and clinical signs	Samples for diagnosis*	Methods
Viruses	Adenoviruses	All, esp. bearded dragons	Liver and GIT, in some cases CNS signs	CS, tissues (liver and intestine)	PCR
	Herpesviruses	Various	Liver, skin, oral mucosa	OS, CS, tissues	PCR
	Iridoviruses	Esp. bearded dragons, chameleons, others, also feed insects (crickets)	Skin, GIT	Tissues (not CS since virus can originate from feed insects)	PCR, VI
	Nidoviruses	Shinglebacks, others	Upper respiratory tract	OS, tissues	PCR
	Paramyxoviruses (ferlaviruses)	Various	Esp. respiratory tract	Tracheal wash, OS, CS, tissues	PCR Sero: HI
	Ranaviruses	Various	Skin, liver, other tissues	Tissues samples; OS and CS not sensitive	PCR, VI
	Reoviruses	Various	Respiratory tract, GIT	OS, CS, tissues	PCR, VI
Bacteria	Bacteria (aerob and anaerob)	All	Many facultative pathogens, can affect various tissues	Samples from lesions. Interpretation in conjunction with clinical signs	Culture
	Chlamydia	Various	Granulomas, pneumonia, myocarditis, hepatitis, others	OS, CS, affected tissues	PCR
	Devriesea agamarum	Esp. Uromastyx spp., others	Skin (cheilitis)	Skin	Culture
	Mycobacteria	All	Esp. granulomas	Material from lesions	Histo, ZN
Fungi	Encephalitozoon pogonae	Bearded dragons, other microsporidia described in other species	Liver, others, granulomas	Faeces, CS, tissues	PCR
	Nannizziopsis spp.	Various, esp. agamids	Skin, in some cases systemic disease	Skin	Cult, histo
	Fungi and yeasts (others)	All	Many facultative pathogens, can affect various tissues	Samples from lesions. Interpretation in conjunction with clinical signs	Culture
Parasites	Cryptosporidia	Various, common in leopard geckos	Esp. intestine	Faeces, CS	PCR, ZN, IFAT
	Parasites (others)	All	Esp. GIT, inapparent carriers to severe infestations and death	Esp. faeces	N, flot

*The ideal sample depends on the stage of infection, type of pathogen, and host species and should be chosen based on the clinical question. CNS = central nervous system; CS = cloacal swab; flot = flotation; GIT = gastrointestinal tract; HI = haemagglutination inhibition; histo = histology; IFAT = immunofluorescence antibody test; N = native; OS = oral swab; Sero = serology (antibody detection); VI = virus isolation in cell culture; VN = virus neutralisation test; ZN = Ziehl-Neelson stain