Gerbils (Laboratory) - Pathology

Introduction

Gerbils are part of the sub-family Gerbillinae which is part of the Rodentia order. There are approximately 100 species of gerbil in 14 genera from all over the world but in laboratory testing, as well as for keeping as a pet, the mongolian gerbil is the most common. The mongolian gerbil or 'jird', Meriones unguichulatus is commonly used for these purposes as they are known for having several characteristics that make them desirable over other species of gerbil. These inclue a very non-aggressive nature, a lower incidence than other species of spontaneous disease, a lack of odour and a monogamous mating behaviour. Some other species have been used for testing, although this is not common. The mongolian gerbil was introduced as a laboratory testing animal in 1963, although they only make up 0.5% of the total number of laboratory rodents used annually.

Strains and Stocks

The gerbil is not commonly used in laboratory testing and therefore when compared to the number of strains of other animals such as the rat, there are few specific strains in gerbils. The most common strain is predominantly agouti, but some black can be found within this strain also.

Physiology

The normal life span of a gerbil is between 2 to 3 years and the adult body weight is 50 - 90 grams. Males are slightly larger than females. Please find details of gerbil physiology within the WikiNormals section. Physiological information available includes “General”, “Biochemical”, “Haematological” and “Breed” parameters.

General Behavioural Characteristics

Gerbils do not have cheek pouches like hamsters but they do exhibit very pronounced hoarding characteristics and it has been found that even under controlled temperature, humidity and day-length conditions gerbils will engage in extensive hoarding behaviours. In their natural habitat, gerbils dig out burrows that can be up to 170cm deep and can extend horizontally for up to 8 metres. These underground complexes often contain nests, hoarding chambers and connecting tunnels. Therefore laboratory housing for gerbils should take both the hoarding and burrowing behaviours into consideration.

Some laboratory studies have found that under laboratory housing conditions, gerbils may develop a stereotypic digging behaviour. An example of this would be digging at the corner of the plastic housing container despite there being no material to move from the plastic. Changes in the housing parameters such as vastly increasing the housing size or the provision of natural substrates such as sand or soil has been shown to prevent this stereotypic digging behaviour. This behaviour often develops in juveniles. It has been shown that the provision of housing with burrows or a tiered tunnel structure can help to reduce this behaviour.

Gerbils are a social species and in the wild group sizes range from 2 to 15. There is usually only one actively reproductive male and female per group. The formation of new groups can be problematic when introducing adults to one-another due to issues of dominance and it is much better tolerated when introducing new juveniles to one-another. Adults will display strong xenophobic reactions towards unfamiliar animals including grinding their teeth and lashing their tails.

Gerbils have a strong desire to scent mark their territory by depositing sebum from their ventral scent gland, urine and faeces.

Integument System

Nasal Dermatitis (Sore Nose)

Nasal dermatitis is a relatively common problem in gerbils, with the incidence higher in younger animals. Although the etiology of this disease is unknown, it has been associated with trauma, stress or accumulation of secretions within the 'Harderian gland'. Bacterial infections with Staphylococcus species have also been linked.

Clinical signs for nasal dermatitis include frequent scabbing and/or ulcer formation, alopecia, erythema and dermatitis. The perinasal area is usually most affected which the periocular region becoming involved in more chronic cases. A very well established dermatitis can spread to the remainder of the head, forelimbs, chest and abdomen.