Hamsters (Laboratory) - Pathology

()Map LABORATORY ANIMAL PATHOLOGY (Map)

Introduction

Hamsters are now commonly used in laboratory testing, but for many years other species including mice, rats and guinea pigs were used for studies requiring small easily managed animals. In 1919 the first study using hamsters was undertaken assessing the susceptibility of Chinese hamsters to leishmania. A number of difficulties were encountered including an inability to breed the animals and hamsters were not used again until the 1930s when a Syrian hamster burrow was uncovered by an archaeologist near Aleppo. Nearly all common hamster breeds are related to these wild discovered hamsters. Syrian hamsters (Mesocricetus auratus)were used and were found to be easier to breed and had more desirable traits for laboratory testing than Chinese hamsters. Syrian hamsters have gone on to become the most commonly encountered laboratory hamster species with around 500,000 per year currently used in the US. However, approximately ten times more mice and rats are used compared to hamsters.

Strains and Stocks

Although Syrian hamsters Mesocricetus auratus or Golden hamsters are the most commonly encountered laboratory species, a number of other species are also used. These include the Chinese hamster Cricetus cricetus, the Armenian hamster Cricetulus migratorius, the Dzungarian hamster Phodopus sungarus and the South African hamster Mystromyx albicauafus. There are a number of differences between these types of hamster;

Breed	Description
Syrian/Golden	Compact body, short legs, 4 front toes, 5 rear toes, 120g, approximately 15cm long, short tail, dark ears, females larger than males.
Chinese	usually grey with a black stripe down its back, 30-35g.
European	usually has a black bely
Dzungarian	varieties include siberian, dwarf, striped and hairyfooted. 30-35g. Summer coat is brown and winter is white.
South African	usually white tailed.

Physiology

Please find details of hamster physiology within the WikiNormals section. Physiological information available includes “General”, “Biochemical”, “Haematological” and “Breed” parameters.

General Behavioural Characteristics

In particular, Syrian hamsters are solitary and only tolerate company when breeding. Females are easily disturbed and aggressive when lactating or pregnant and in such situation can be prone to kill other hamsters. Cannibalism is common in stressed primiperous females.

Anatomy and Histology

This section has been included to allow familiarisation with the peculiarities of hamster anatomy to provide a context for some of the disease and pathological headings found below. Therefore only anatomical areas with specific features warranting emphasis have been included below;

Integumentary System

Hip/Flank Glands Sebaceous glands with pigmented cells and terminal hairs that secrete during sexual arounsal in both sexes. Also used for olfactory territorial marking.

Reproductive System

Vaginal Discharge Post-ovulatory dimethyl disulphide is used as a breeding tool by females but is often mistaken for an inflammatory exudate due to its similarity in smell to rotten eggs.
Sexual Dimorphism Male Syrian hamsters have much larger adrenal glands than females despite females being generally larger than males.
Fostering Newborn This is not usually possible in hamsters as infants are extremely immature when born and 'foreign' infants usually do not accept one another.

Urinary System

Kidneys Extremely long papillae extending into ureters. Very developed water conservation systems.

Cardio-Respiratory System

Heart The Purkinje network and sino-atrial node are easily accessible surgically and is a useful physiological feature for some experiments.

Digestive System

Cheek Pouches Hamsters have highly distensible evaginations of the lateral buccal walls which are used to store and transport food.
GI Physiology Long duodenum, long jejunum, short ileum, big cecum, long colon.
Stomach Distinct constriction between the forestomach and glandular stomach. No lesser curvature of the stomach resulting in two blind sacs. Pregastric fermentation occurs in hamsters.
Cecum Apical an basal portions seperated by a semilunar valve. There are a series of 4 valves in the ileocecolic area.

Diseases

For ease of use, the diseases of hamsters listed below are by body system, or where this is not appropriate in an “Other” category displayed after the body system sections. Those diseases listed below are not exhaustive but rather highlight common diseases encountered with laboratory hamsters.

Integument System

Reproductive System

Urinary System

Respiratory System

Digestive System

Infectious Causes of Diarrhoea

Salmonella
Salmonella typhimurium and Salmonella enteriditis are the common causative agents and are often associated with contaminated food and bedding. Diarrhoea may be haemorrhagic, cause septicaemia and can also cause sudden death.

Parasitic Causes of Diarrhoea

Nematodes

Musculoskeletal System

Other