Hamsters are a domestic pet native to south east Asia and Europe. The first female and 11 pups were brought to a university in Jerusalem, and from the surviving four littermates, the entire domesticated world population of hamsters was developed. Syrian hamsters were brought to the United States of America in 1938 (Vinerean, 2023).
Natural behaviour
In 2014, approximately 500 000 hamsters were kept as pets in the UK, according to estimates from the Pet Food Manufacturers Association (Mancinelli and Bament, 2014). There are many breeds of hamsters, including Chinese, Teddy and Russian, but the most common is the Syrian or Golden hamster (Figure 1). The Syrian hamster is a typically nocturnal species like all rodents, and they must not be kept in groups or pairs because of their territorial nature. Females are generally more aggressive than males and keeping them in groups, whether in a domestic or veterinary environment, can lead to aggression and risk of injury (Lennox and Bauck, 2012; Elidio et al, 2021).
Anatomy and physiology
Hamsters are generally herbivores, although they can be considered omnivorous. They mainly feed on seeds, grains, nuts, fruits and vegetables, but occasionally eat insects and lizards (American Tarantula and Animals., 2023). When providing nutrition within the veterinary clinic, pelleted diets are generally recommended with fresh water being freely provided. Muesli diets are avoided as this can lead to selective feeding (the ‘behaviour’ by which an animal chooses which parts of the diet or mix provided is preferred, usually because of the taste preference of the particular animal. This can lead to lack of certain nutrients and dietary concerns.).
It is outside the scope of this article to go into great detail, but a brief description of the anatomy of the hamster is provided. The most prominent and probably well-known feature of the hamster is their cheek pouches - simply invaginations of the oral mucosa found in the lateral buccal walls (Miedel and Hankenson, 2015). These are highly distensible pouches, used for temporary storage of bedding and food. Hamsters have a two-compartmented stomach and a ‘pre-gastric pouch’, as well as a sensitive digestive system, so correct dietary provision in the veterinary environment is extremely important (Clarke, 2023).
Housing provision in the veterinary environment
Hamsters (especially Syrian) are a typically solitary species, as previously mentioned, and highly prone to stress. When housed in the veterinary environment, it is extremely important to minimise stress levels by housing them in an area that is away from the sight and smell of predators. Ideally they should be kept at temperatures around 20-22°C (Mancinelli and Bament, 2014; Clarke, 2023) and 40-60% humidity, as they do not have sweat glands and are unable to pant, so do not have an efficient method of temperature control.
These species can live in an area of several kilometres in the wild, and should be given ample well-ventilated space, with a deep layer of substrate to facilitate natural burrowing behaviour (Royal Veterinary College, 2022). Hamsters are experienced climbers so care should be taken to make the housing area safe from hazards, as well as providing toys and environmental enrichment, and a nest box with appropriate bedding material. This should ideally be recyclable material or paper, as cotton wool can be easily impacted in their cheek pouches (Royal Veterinary College, 2022).
The cages should be cleaned out regularly to ensure bedding areas and toileting areas are clean, to remove hoarded food, and prevent diseases such as wet tail and respiratory issues from dusty bedding such as sawdust or shavings.
When housed in the veterinary environment, it is important to consider the condition that the hamster has been admitted for. Be aware that humidity can worsen or cause respiratory symptoms and that temperatures less than 5-6°C will result in the hamster hibernating, which will slow respiration and heart rate, making it difficult to monitor them either in the standard medical environment or postoperatively following surgery. Temperatures must not exceed 20-30°C as this will result in hyperthermia and death. Kennel/cage selection and placement must be considered as mentioned earlier because of the predator/prey scenario and also the risk of injury associated with wire cages.
Common ailments and illnesses
Hamsters have specific needs and requirements, and can be presented to the veterinary clinic with many different ailments and conditions. It is important to understand how to best care for and manage these in the veterinary clinic.
Some of the most common ailments include ectoparasites (most commonly Demodex criceti and Demodex aurati) as well as both fungal and bacterial conditions. Hamsters commonly develop skin tumours as well as cheek pouch disorders such as impaction or prolapse. They can experience endocrine issues caused by a chromophobe adenoma in the pituitary gland, as well as gastrointestinal and respiratory issues (Girling, 2013). Strict hygiene standards must be maintained; although the risk of zoonotic disease transmission is low, the most common are lymphocytic choriomeningitis virus and hantavirus, which are usually transmitted via urine or saliva (Brament, 2015).
One of the most common diseases that hamsters are presented to the veterinary practice for is ‘wet tail’, which is also referred to as proliferative ileitis. Caused by Lawsoma intracellularis, an intracellular bacterium, it is the most significant intestinal disease of 3-10-week-old hamsters and has a high mortality rate (Brown and Donnelly, 2012). Treatment is aggressive and involves correcting electrolyte imbalances, administering antibiotics and feeding. The exact treatment is outside the scope of this article, but there are several options available (Brown and Donnelly, 2012).
Although hamsters are generally very well equipped for cooler weather and will generally hibernate, digging deep burrows and tunnels to stay warm. In very cold temperatures they will struggle to maintain their body temperature and can freeze to death if left unchecked. This is especially important to consider in the veterinary environment as factors such as air conditioning, and the fact that they are unwell and therefore not able to manage their temperature as well, can increase their risk. They also need a plentiful food supply and although they will wake up periodically to eat, if they are kept warmer then they will likely not need to wake and feed as much. They require more calories to stay warm and can easily become overweight, so it is important to monitor this while in the veterinary environment (Hillcrest Animal Hospital, 2018).
Anaesthesia and postoperative care
It is important to be aware of the procedures and risks that are associated with these species when performing procedures and monitoring anaesthesia. The most common anaesthetic protocol used is isoflurane or sevoflurane in a chamber. A less common protocol used is ketamine 100 mg/ml (5 ml), xylazine 20 mg/ml (2.5 ml) and acepromazine 10 mg/ml (1 ml) (McGill University, 2021). Vivien et al (1999) looked at the minimum alveolar anaesthetic concentrations of isoflurane or sevoflurane, as well as halothane and desflurane, and found that the minimum alveolar anaesthetic concentrations were significantly lower in cardiomyopathic hamsters than in healthy hamsters. A further study showed that the anaesthetics produced no significant shift in the voltage dependence of activation in terms of sodium (Na+) gated channels (Ouyang et al, 2009).
Veterinary nurses must also remember that because of their size, hamsters have a high metabolic rate and demands. Therefore, it is important that nutrition is maintained, especially as they can develop hypoglycaemia following periods of anorexia (Brament, 2015). Mean arterial blood pressure can also be monitored through the arterial catheter connected to a pressure transducer (Villela et al, 2014). Low temperatures and hypothermia can affect the uptake of inhalant anaesthetic gases.
Fluid therapy and blood collection
When hospitalised, it may be necessary to collect blood samples to test externally or in house. It is important to carefully weigh the benefits of obtaining a blood sample against the stress of the collection process, especially stress caused by handling (Nugent Deal, 2010). Unless clinically contraindicated, it is generally advised to use anaesthesia or sedation to minimise the stress of handling and venipuncture, while remembering that anaesthesia can affect test results usually as a result of the stress causing release of glucocorticoids and suppression of the immune function (Jasnow et al, 2001).
In terms of methods of sampling, sublingual bleeding is the preferred method to retrobulbar bleeding, because of the necrosis and damage caused during the sampling technique. This could be caused by the location or the method of obtaining a sample. The oral cavity of the hamster is fairly wide and the sublingual veins have a larger diameter, so there is a reduced risk of tissue damage; this is also a simpler procedure (Heimann et al, 2009). In small animals, the lateral saphenous vein can be used for blood collection (Nugent Deal, 2010). Increasing body temperature to aid vasodilation, using a heating pad or incubator to warm the cage for up to 10 minutes, can help with blood collection. It is also possible to dilate tail vessels, consider sedation or isoflurane or sevoflurane anaesthesia to minimise stress and also use topical agents or sedation with midazolam (0.25-1.0 mg/kg/intramuscularly) (Nugent Deal, 2010). However, as hamsters usually have a small tail area, this is most likely not the best or safest option. Additionally, if assisting with venipuncture or laboratory analysis, the blood must be used quickly, as Syrian hamsters have a relatively low prothrombin time, meaning that whole blood clots quickly at room temperature. The total volume of blood typically taken to test ranges from 0.5-1.0% bodyweight. Microtainers must be used to place the blood (Hem et al, 1998).
Owner advice
Whether it be a postoperative discharge or following inpatient care, it is important to make sure that the owner is aware of the signs to look out for in case further treatment is needed. Debilitated small rodents may well exhibit signs such as hunched posture, piloerection of fur guard hairs, anorexia, general lethargy, chromodacryorrhoea, laboured breathing, vocalisation with or without stimulation, shivering, ataxia and production of abnormal amounts of urine and faeces (Brament, 2015).
Conclusions
This article has highlighted the importance of monitoring hamsters and small rodents when in the clinic. It has also outlined their behavioural traits, nutrition and physiological traits that can predispose them to higher anaesthetic risks, hypoglycaemia and increased mortality rates. It is important to maintain knowledge and skills and educate owners as part of the role as a veterinary nurse.
Key points
- Hamsters are a solitary species highly prone to stress and care must be taken to ensure that their needs are met while in the veterinary clinic.
- Although injectable agents can be used for anaesthesia, these are not generally commonplace and sevoflurane or isoflurane is generally considered the best option to use.
- Owner education is extremely important to ensure that they are aware of the signs to look out for so hamsters receive the quickest and most appropriate treatments and care.