Table of Contents

Whole Allergen

e74 Rat urine proteins

e74 Rat urine proteins Scientific Information

Type:

Whole Allergen

Display Name:

Rat urine proteins

Route of Exposure:

Inhalation

Family:

Muridae

Species:

Rattus spp.

Latin Name:

Rattus

Other Names:

Rat

Summary

Urine proteins of rodents, including Rattus spp. (rat), are inhalant allergens that cause respiratory symptoms in sensitized individuals. In addition to being common pets and ubiquitous pests, rats are commonly used for scientific research. As such rat urine protein allergens are an important cause of allergic respiratory disease, particularly occupational disease in laboratory workers.

Allergen

Nature

In addition to being common urban and rural pests, rats are kept in homes as pets and in laboratories as animal models in scientific research (1); in 2014, rats accounted for 7% of the 3.8 million animals used for scientific research in Great Britain (2).

The sensitizing agents in rats are proteins found in their urine and saliva (2). These proteins contaminate their fur and fomites and are readily aerosolized by husbandry practices (2).

Urine is such a potent source of rat allergens because rats have permanent proteinuria (males have particularly high protein levels in their urine) and perform behavioural enurination. When the urine dries, proteins associate with airborne dust particles and can be inhaled, leading to sensitization. (3).

Reported prevalence rates of allergies in laboratory technicians working with laboratory animals range from 11% to 30% (4).

Taxonomy

*Taxonomic tree of Rattus* (5)**
Domain	Eukaryota
Kingdom	Metazoa
Phylum	Chordata
Subphylum	Vertebrata
Class	Mammalia
Order	Rodentia
Family	Muridae
Genus	Rattus

Epidemiology

Worldwide distribution

Exposure to laboratory animal allergens is a significant cause of IgE-mediated occupational allergy and asthma in the pharmaceutical sector, contract toxicology laboratories, research institutes and universities (2); reported prevalence rates range from 11% and 30% (4).

In a study of 101 laboratory animal technicians, 30% had symptoms (100% had rhinitis; 10% had concurrent bronchial asthma), and 19% had confirmed allergy (4). In the same study, 18% of laboratory workers exposed to rats, had confirmed allergy (4). All the rat-sensitized individuals had been working with mature male animals (4).

In a study of occupational sensitization to rat and/or mouse urinary allergens, out of 498 employees exposed to both rat and mouse at work and 220 exposed to rat only (6), 14% were sensitized to rats.

Risk factors

Exposure to rat urine in the workplace, especially research laboratories (2), or in the home (1).

Some handling and husbandry activities are associated with high exposures (2). For example, filtered cages may reduce exposure, while filter changing and/or cleaning can lead to high exposures (2). Equally, continued contact with animals may raise sensitivity; mild symptoms may serve as a precursor to a warning for the risk of developing bronchial symptoms (4).

A history of atopic disease; in one study, atopy was overrepresented in technicians with positive RAST and skin test reactions to the animal allergens compared with technicians without positive tests (4).

Route of Exposure

Main

Inhalation (3).

Secondary

Contact (4).

Clinical Relevance

Symptoms of sensitization to rat urine proteins include rhinorrhea, nasal congestion, sneezing, conjunctival itching, cough, dyspnea, wheezing (4) and, rarely, anaphylaxis (2). Itching and skin weals may also occur at contact sites (4).

Molecular Aspects

Allergenic molecules

The following allergens have been identified from rat urine and serum (table adapted from Allergome.org (7)).

Allergen	Type	Mass (kDa)
Rat n 1	Lipocalin (α2u-globulin)	21
Rat n 4	Albumin	69
Rat n 7	Immunoglobulin; IgG	94
Rat n Transferrin	Serotransferrin	76

Cross-reactivity

In a study of occupational sensitization to rat and/or mouse urinary allergens, 62% of rat-sensitized individuals were also mouse-sensitized, while 91% of mouse-sensitized individuals were also rat-sensitized (6).

Compiled By

Author: RubyDuke Communications

Reviewer: Dr.Christian Fischer

Last reviewed: June 2022

References

Munera M, Contreras N, Sánchez A, Sánchez J, Emiliani Y. In silico analysis of a major allergen from Rattus norvegicus, Rat n 1, and cross-reactivity with domestic pets. F1000Res. 2019;8:1707.
Mason H, Willerton L. Airborne exposure to laboratory animal allergens. AIMS Allergy and Immunology. 2017;1(2):78-88.
Schulten V, Westernberg L, Birrueta G, Sidney J, Paul S, Busse P, et al. Allergen and Epitope Targets of Mouse-Specific T Cell Responses in Allergy and Asthma. Front Immunol. 2018;9.
Agrup G, Belin L, Sjöstedt L, Skerfving S. Allergy to laboratory animals in laboratory technicians and animal keepers. British Journal of Industrial Medicine. 1986;43(3):192-8.
CABI. Rattus (rats) Wallingford, UK 2019. Available from: https://www.cabi.org/isc/datasheet/46827.
Jeal H, Harris J, Draper A, Taylor AN, Cullinan P, Jones M. Dual sensitization to rat and mouse urinary allergens reflects cross-reactive molecules rather than atopy. Allergy. 2009;64(6):855-61.
Allergome. Rat urine proteins. 2022.