Viral diseases in snakes which pathogens are of importance pmc

Viral diseases in snakes – Which pathogens are important??Correspondence address Dr. Annkatrin Neul Additional title Reptiles, Clinic for Birds and Reptiles, Faculty of Veterinary Medicine, University of Leipzig, An den Tierkliniken 17, 04103 [email protected]

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Ferlavirus infection

The disease with ferlaviruses is a highly contagious viral infection, which is often characterized by a fatal outcome. Ferlaviruses have been detected in snakes, but also in lizards and turtles. However, these pathogens play the most clinically relevant role in snakes, where the disease has a epidemic course can be amed. Ferlaviruses belong to the family Paramyxoviridae. Are also known as ophidian paramyxoviruses.

Commonly affected species include:

Especially with the Rattlesnakes ( Crotalus spp.) ames the presence of the disease dramatic course at. The tenacity of the virus itself is only low.

About the ways of transmission of the ferlaviruses is still relatively little known. However, a predominantly aerogenic or. oral transmission is suspected, since the virus is excreted via secretions and feces. There are no studies on vertical transmission routes so far.

Also the Pathogenesis of the ferlaviruses is not yet fully understood. Predominantly the cells of the lung tie and the central nervous system are attacked, which is confirmed by the manifestation of the typical clinical symptoms. However, the virus is able to infect all internal organs in the course of the infection.


Ferlavirus infections are often associated with highly pathogenic disease outbreaks. In snakes occur respiratory Symptoms such as respiratory distress ( Fig. respiratory sounds. Exudate from the trachea ( Fig. 2 ) and neurological Suffering, z. B. abnormal posture, tremors and convulsions. However, there have also been unspecific symptoms as anorexia and emaciation described. Usually, in the early stages of infection, no clinical symptoms are evident despite the presence of disease. Not infrequently sudden deaths before. Secondary bacterial or mycotic infections, especially of the lungs, are also common. This makes the clinical picture even more dramatic. First sign of a secondary infection is usually stomatitis.

High-grade dyspnea in snakes is manifested by a torn mouth, a flared tracheal opening, and a hyperextended anterior third of the body.

viral diseases in snakes which pathogens are of importance pmc

Serous exudate (arrow) in the throat of a royal python ( Python regius ) due to a ferlavirus infection.


Virus detection is essential to confirm suspected ferlavirus infection. For this purpose the detection by specific molecular biological methods (PCR) is recommended, but virus isolation by cell culture is also possible. Suitable examination materials are Throat- and Cloacal swab . However, even more reliable is the examination of the Tracheal secretions , that can be transmitted with the help of a tracheal lavage ( Fig. 3 ) can be obtained.

Procedure for tracheal lavage sampling. a For tracheal lavage in snakes, a sterile lavage probe and syringe are required. As an irrigation solution, warmed 0.9% NaCl solution (max. 10 ml/kg) should be used. b With the help of another syringe, the mouth can be opened gently, allowing the tracheal opening to be seen. c The flush probe should first be fixed at the anterior end to allow easier insertion. d Now you have to wait until the snake breathes on its own and opens the trachea. This may take some time. During a breath, insert the irrigation probe and advance it carefully. Now apply the lavage fluid slowly, keeping the snake horizontal. e Then hold the animal upside down and, while recovering the rinsing liquid, carefully pull out the rinsing probe again at the same time. Afterwards, the snake should be held upside down for some time to allow the excess residual fluid to drain out of the lungs. The rinsing fluid obtained can now be assessed macroscopically. Further diagnostics can be performed.

Also the examination of the Blood for the presence of antibodies is possible. However, detectable titers vary widely, so these results must be supported with additional viral detection. Therefore, if a titer is present, additional PCR is always recommended. Serological examinations can be performed in the context of a Stock screenings to find out whether there has already been contact with ferlaviruses. For this purpose, all animals should first be sampled. Pooled samples (composite samples from multiple animals) can be tested to save costs if necessary. If suspect pool samples are found, the affected animals should then be retested individually to evaluate which animals are positive.

In the pathological examination in snakes mainly changes in the respiratory system are detectable. Macroscopically, exudative pneumonias are common, as are congestive. Determine hemorrhagic changes in the lungs ( Fig. 4 ). In advanced stages, the serous exudate leads to obstruction of the lumen of the lungs and air sacs, thickening of the lungs, and pulmonary edema. Furthermore, white nodular changes of the liver parenchyma, hepatomegaly, enlargement of the pancreas, pancreatic necrosis and fibronecrotic exudates in the celomic cavity can be observed.

Macroscopic findings caused by ferlaviruses in the pathological examination of a snake's lung: highly thickened, red-white marbled lung with yellow foamy-fluffy contents (lung cut open lengthwise, view of lung interior/lumen).

In some cases, however, no macroscopically detectable changes occur at all.


If a ferlavirus infection is suspected, a pathological-histological examination is also recommended.

The histological changes range from hyperplasia of the respiratory epithelium to diffuse interstitial infiltrates of lymphocytes, heterophils, plasma cells and macrophages. In addition, in some cases intranuclear or intracytoplasmic viral inclusion bodies can be detected, which are attributed to the ferlaviruses and can be visualized by immunohistochemistry. When neurological symptoms occur, demyelination and degeneration of axons take place, resulting in histologically detectable axonal distortion. In addition, meningoencephalitides occur, in which the glial cells may also show intracytoplasmic inclusion bodies.

Arenavirus infection

The so called inclusion body disease (IBD) is a worldwide and mainly in snakes common disease Boids disease that occurs. Rarely this disease is also observed in pythons. Individual cases have also been reported in March's palm lance snakes ( Bothriechis marchi ). An eastern chain snake ( Lampropeltis getula ) described. Overall, inclusion body disease is the most important viral disease of boids.

Etiology and pathogenesis

The disease is caused by formation from intracytoplasmic inclusion bodies characterized in neurons and epithelial cells of different organs. These inclusion bodies consist of a protein. Currently, arenaviruses are thought to be the cause of the disease, with the viruses detected forming a genetic variability and several different viruses have been found so far.

The transmission occurs via direct contact and excrement. But also snake mites and the movement of food animals or cleaning and maintenance work to be carried out in various terrariums are suspected as transmission possibilities. The pathogenesis, however, is still unclear.


The inclusion body disease leads in boids and pythons to a Immunosuppression . Therefore, the clinical symptoms often associated with the disease vary widely. These can be detected by subclinical carriers up to severe neurological deficits and lead to death. disorders. vomitus before. mortality rate is up to 100% in this case. In addition, some infected snakes die within weeks; others survive the infection for longer periods of time.

Subacute or chronic disease progression however, is observed in older animals and pythons. In most cases, nonspecific symptoms such as respiratory distress, anorexia, or vomiting occur.


In existing disease, the intracytoplasmic inclusion bodies may already be present in the peripheral blood be detected. However, this is only possible in boids. Poorly stained blood smears resp. Buffy coats can be a problem. This is caused by the sometimes poor staining of the inclusion bodies with the common Romanowsky stain. This also plays a role in cytological examination of liver aspirates plays a decisive role. This means that a pathological-histological examination of a liver biopsy may be necessary ( Fig. 5 ).

detection of intracytoplasmic inclusion bodies ( * ) during pathological-histological examination of the spleen tie of a Boa constrictor.

At Pythons the inclusion bodies are only present in the Brain ( Fig. 6 ), which makes intravital diagnostics difficult. Therefore, a virological examination (PCR) is necessary in this case of Throat- and Cloacal swabs recommended.

Pathological-histological examination of the brain: evidence of inclusion bodies (arrow).


The differential diagnosis must be based on an infection with ferlaviruses, which occurs more frequently in pythons in connection with central nervous symptoms.

Nidovirus infection

Nidovirus is a relatively new virus that was discovered in 2014. So far these viruses could not be found in King pythons (Python regius) and in Tiger pythons (Python molurus) with pneumonias and stomatitis being detected relatively frequently. However, more research is needed on this viral infection.

Etiology and pathogenesis

Nidoviruses belong to the Torovirinae subfamily of the Coronaviridae family. The nidoviruses found in king pythons (Python regius) are called "ball python nidovirus" (BPNV). These RNA viruses predominantly infect the upper and lower respiratory tract, but virus detection has also been possible in the gastrointestinal tract. Also mixed infections with other viruses (Ferla-, Reoviruses) are described. On the whole, however, relatively little is yet known about the transmission pathways. The pathogenesis of nidoviruses known.

Clinic and diagnosis

Until now, nidovirus infections were usually treated with pneumonias and Stomatitis associated. The lung infections range from proliferative interstitial to necrotizing pneumonia. Additional secondary bacterial infections also frequently occur, also restricted to the respiratory and gastrointestinal tracts.

In the pathological-histological examination hyperplasia of the epithelium with inflammatory infiltrates, but also necrosis is possible.

Therapy, prognosis and prophylaxis

As with most viral infections, specific therapies against ferla, arena and nidoviruses are not possible based on current scientific knowledge. Therefore a symptomatic therapy in the foreground. Life-prolonging measures may include immunostimulants, z. B. Zylexis ® (up to 1 ml/animal i. m. every 14 days), should be used. Possible secondary bacterial infections should also be treated specifically with a broad-spectrum antibiotic, z. B. Enrofloxacin (Baytril © 8 – 10 mg/kg i. m., s. c. every 24 h, over 7 – 14 days) are treated. However, this type of therapy is also not promising in the long term after the onset of the clinic.

Once clinical signs have clearly manifested, the Prognosis and euthanasia is recommended. If the causative virus is detected, euthanasia is inevitable.

In one Ferlavirus infection However, the detection of the viruses alone does not mean that a clinic must manifest itself. However, there is a risk of infecting other snakes. On the other hand it is described that Arenavirus-infected snakes may be able to survive the infection without developing inclusion body disease. If the Inclusion body disease If there is evidence that the virus exists in a herd, the herd must be separated and contact with other herds must be avoided. In addition, sanitation of the flock should be considered, which can be achieved by restocking after green cleaning and disinfection.

Due to the difficult therapy of an existing viral infection, preventive measures are recommended. Therefore, adherence to Quarantine periods particularly important in the case of new stock. Quarantines of up to 6 months must be adhered to.


Viral diseases play an important role in snakes. The ferlaviruses are of particular importance, but arenaviruses are also among the most important viral pathogens in Boiden. The newly discovered nidovirus is also becoming increasingly relevant. Since there is no causal therapy to cure most viral infections, prophylactic measures in the form of quarantine periods for newly acquired animals are of crucial importance to build up healthy snake populations. Sunshine virus also belongs to the paramyxoviruses. Is therefore distantly related to the Ferlavirus. So far, these viruses have been found mainly in pythons in Australia, which showed respiratory and central nervous symptoms. Accordingly, the Sunshine virus, like the ferlaviruses, causes changes in the lungs and the central nervous system. pathogen is not very stable in the environment. Can therefore be easily disinfected. Here, too, PCR detection or. Virus isolation by cell culture from pharynx-. Cloacal swabs or tracheal lavage samples possible. However, the most reliable detection has so far been obtained from brain material. Serological detection methods, on the other hand, have not yet been described. Therapeutically and prophylactically the same measures have to be taken as in case of a ferlavirus infection.

Other viral infections

Infections with other viral pathogens are also sometimes described in snakes, but play a rather minor role.

The most frequent Reovirus infection which occurs in snakes in association with pneumonia, gastrointestinal and central nervous symptoms. Among others, reoviruses have already been detected in Chinese vipers (Azemiops feyi) with enteritis, in a western rattlesnake (Crotalus viridis) with central nervous symptoms, and in rough grass snakes (Opheodrys aestivus) with necrotizing hepatitis. Reoviruses are also frequently found as co-infectious agents in inclusion body disease.

Also Adenovirus infections Occur in snakes and are seen in association with disorders of the gastrointestinal tract. The so-called snake adenovirus (SnAdv) has been found in abbots (Boa constrictor) and king pythons (Python regius), among others. However, it was also possible to associate snake adenovirus-1 with clinical signs of pneumonia in a corn snake (Pantherophis guttatus).

All other viral infections detected in snakes are mainly single case reports. For example, gastrointestinal symptoms in a four-striped snake (Elaphe quatuorlineata) and an Aesculapian snake (Elaphe longissima) have been associated with Parvoviruses associated with. Bottle snake (Boa constrictor). Described an Aesculapian snake (Elaphe longissima). Furthermore Caliciviruses found in Aruba rattlesnakes (Crotalus unicolor), in a rock rattlesnake (Crotalus lepidus), and in a prehensile-tailed lance snake (Bothriechis schlegelii), among others.


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