Rodents, so called because of their habit of “nibbling”, are an order of mammals that currently includes more than 2200 species, some of which (in this case those belonging to the family of the Muridi) are synanthropic and commensal species of man, that is, they have adapted to share the habitats occupied by man and to exploit the food resources.
It is very important to be able to recognize the presence of Rodents in an environment, in order to be able to proceed with a timely deratization intervention. What are the most common types of Rodents (Rats and Mice) in Italy? Let’s learn to know them to fight them better!
TOPOLINO DI CAMPAGNA (Mus musculus): slender body, pointed snout, big ears, very small eyes. It is a lively animal with a very fast metabolism so it is always at the top of its game.
Although it is more active at night, precisely because of its dietary needs, it is often visible even during the day, although it shows prudent behaviour towards man.
He prefers the houses where he lives and nests, choosing places that tend to be warm and dry (attics, wall cavities, furniture, barns, spaces under the floors). It forms dens using fabric shredder, paper, grass and similar materials.
Thin, pointed faecal traces the size of a sesame grain.
It reaches sexual maturity at 2-3 months of life and gestation lasts from 18 to 21 days; each female has 4-5 (up to 10) pregnancies per year with 4-10 births per birth (about 50 per year).
Infestations cause serious damage in agriculture and rural areas (plantations) but can also represent a serious health and hygiene problem inside houses and economic activities as excrements and urine are a source of contamination for objects and food.
KEY RATCH OR STEAM PANTEGANA (Rattus norvegicus): stocky body, rounded snout, small ears, small eyes, tail length shorter than the remaining body length.
Very active and, if necessary, aggressive species living in communities of blood relatives organized in patriarchal societies. Active mainly during the night, it is very habitual, therefore it nourishes and frequents always the same places.
Excellent digger and swimmer who adapts to many environments, preferring however humid places (ditches, sewerage networks, underground areas).
Stumpy faecal traces similar to an olive kernel
It reaches sexual maturity at 70-80 days of life and gestation lasts 21-24 days; each female has 4-5 (up to 8) pregnancies per year with 8-12 births per birth (about 38 per year).
Infestations represent in all cases a serious health and hygiene problem as sewer rats are a reservoir of many diseases communicable to humans and pets.
ROOF RAT OR BLACK RAT (Rattus rattus): slender body, pointed snout, large ears and eyes, dark back and light abdomen, tail length exceeding the length of the rest of the body.
It lives in colonies, whose number is often linked to the amount of food available. It has behaviors and eating habits characterized by high distrust and is certainly the most intelligent among the three species of Muridi infesting.
He is a good swimmer but he is above all a very agile climber and shows extreme adaptability to the most diverse environments. In rural areas (farms, barns, food warehouses) his control, in case of infestations, is very complex and should certainly be entrusted to experienced personnel.
Faecal traces similar to those of the sewer rat in size but elongated in shape.
It reaches the sexual maturity when 2-3 months old and the gestation lasts 20-22 days; each female has 5-6 (up to 8) pregnancies per year with 6-8 born per delivery (about 35 per year).
In case of infestations, timely deratization intervention by competent personnel is necessary. This species is considered to be mainly involved in the epidemiology of salmonellosis due to contamination of food and surfaces.
Signs of Rodent presence
In confined environments as well as inside houses, it is possible to detect the presence of mice and rats either directly, or following sightings of living or dead people in internal areas, or indirectly through their signs of presence.
Among the most common signs of presence of the passage of Rodents, those most easily found are certainly the faecal traces, from which it is possible to trace almost always the species of rodent present.
Rats and mice tend to have a shy attitude towards humans and are also active at night, so it is almost always more likely to find the presence of faeces (or urine) in the presence of infestations. These faeces, if produced recently, have a soft but compact consistency and to the touch tend to crush but not to break. They are easily confused with the faeces of other small animals, mainly bats, small reptiles and amphibians which, however, as they tend to be insectivorous, produce faeces that are crumbly to the touch as they contain the undigested chitin of the insects on which they feed.
The faeces of reptiles and amphibians also have traces of urati (white) which clearly distinguish them from those of rodents.
After a period of time (usually more than 24 hours) and depending on environmental conditions, the faeces of rodents become very hard. This is important to understand how long the infestation has been going on and whether there has been a recent passage.
Rodents defecate in the same places where they move, feed or drink, so it is important to identify these signs of presence, always keeping in mind that mice and rats adopt tigmotactic behavior in their movements, i.e. they tend to move along the perimeter of the environment keeping one side of the body in contact with the walls for protection.
Therefore, the presence of faeces and excrements can often be detected along the perimeter of rooms. The faeces of Rats and Mice have characteristics that allow you to trace the species to which they belong.
The Domestic Mouse (Mus musculus) produces thin faeces of reduced dimensions (not more than one centimetre in length) with tapered ends.
The Black Rat (Rattus rattus) has faeces of 1-1,5 cm in the shape of a scythe but with rounded edges.
The feces of the Chiaviche rat or sewer rat (Rattus norvegicus) are larger feces up to 2 cm in length, with a squat shape that often resembles the kernel of an olive.
In any case, it is always advisable to consult an expert in the field for reliable recognition, therefore it is always useful to keep a faecal sample, taking care to always collect the material using disposable protective gloves and placing it in a well closed container.
Other signs of presence are the erosions caused by these animals both in food and other materials such as plastic, cardboard, textiles, various packaging, etc..
An expert technician is also able to detect other signs of presence such as burrows, greasy marks left along the way or footprints on dusty surfaces.
Rodent Friendly Environments
All the listed species share urban and rural environments with man, they feed by eroding food, and have a very flexible skeleton that allows them to access the structures even from very small openings (4 mm in diameter in the case of the house mouse).
In general, however, Rodents prefer sheltered environments, where they can find easy hiding places or escape routes, but especially where it is possible to find food to feed themselves. For this reason, houses and all the structures where food is found are places potentially attackable by Rodents.
How do the Rodents arrive?
Rodents have spread around the world through the movement of goods, they enter a new structure using hidden or not clearly visible access points and are able to teach other people in the colony the routes they use.
Therefore, once a Rat or Mouse enters a structure, they are unlikely to be alone.
The access routes can also take place through electrical or hydraulic systems, through holes in cavities or walls, through high parts such as roofs or windows.
It is also possible that Rodents are transported with goods from infested means of transport or warehouses.
Health risks due to Rodents
Living in contact with these animals, in fact, in addition to creating anxious psychological states in people because of the sense of repulsion that we often feel for them, can be the cause of the spread of pathologies carried by pathogens related to their presence.
Consider that at present the epidemiological involvement of mice and rats concerns about 35 diseases all over the world.
Transmission to humans can occur through direct contact (direct contact with Rodents or their carcasses, bite, contact with urine, faeces, Rodent saliva also due to contamination of water and food).
Indirect (through ticks, lice, fleas capable of transmitting the pathogen from the Rodent to humans).
In case of presence of faeces and urine of Rodents it is necessary to proceed to an appropriate disinfection of objects and structures considering that any food and drink potentially contaminated must be eliminated.
If disinfection requires intervention in confined spaces or in case of accidental entry of a rodent into the house, household disinfectants (chlorine or peracetic acid based) can be used after removal of dirt (faeces).
In very large environments, or in the case of large infestations, disinfection should be entrusted to experts in the field because it is necessary to assess the parameters and characteristics of the environment on which to intervene (e.g. schools, hospitals, clinics, accommodation facilities, food industries, etc. …).
Rodent infestation prevention
The fight against rodent pests must include, first and foremost, strict preventive measures.
Below you can see some aspects that can help to keep rodents away from the facilities where people live or work:
- the external perimeter areas must be paved and adequately drained in order to avoid water stagnation;
- the external perimeter areas, for a strip of 8-10 metres, must be clear of various materials and kept clean;
- for the furthest areas, if not paved, there must be effective control of spontaneous vegetation by mechanical mowing;
- the walls must be as smooth as possible and the fixtures installed on the outer edge, or on the inner edge of the wall but with a sill inclined outwards, so as to hinder climbing;
- all windows and any other openings used for air exchange (including doors) must be fitted with intrusion prevention systems (brushes, thresholds, tyres);
- service doors must be automatic opening and closing so as to reduce opening time as much as possible; it is also possible to equip the openings with automatic double doors (compasses); all other doors must remain closed, including those for communication between departments;
- door jambs and door leaves must be intact and leakproof;
- all manholes for the inspection of underground installations must be closed;
- all cable ducts must be closed (often preferential routes for rodents);
- all holes prepared for the passage of electrical and hydraulic systems must be sealed;
- all drains must be properly siphoned to prevent weeds from ascending and periodically treated to prevent insect proliferation;
- waste must be evacuated from the wards at least once a day and stored in suitable containers as closed as possible; these must be placed in a paved area so as to facilitate cleaning and located in a place far from the plant;
the installations and goods must be lifted off the ground and spaced at least 30-50 cm from the walls, so as to limit the possibility of infestation and allow periodic cleaning and inspections;
- pallets (especially wooden pallets) must not be stacked in the open air, where they absorb moisture, develop mould and host insects which are then transported to the departments;
- departments and machinery temporarily not in use must be well cleaned and covered to protect them from dust, so that they do not become a shelter for insects and rodents;
- staff working on the farms must be adequately informed and trained on the importance of behaviour conducive to hygiene and cleanliness.
Problems related to Restaurants and the Food Sector
The regulations on self-control including EC Directive n°93/43 and D.L. 155/97, now replaced by EC Reg. 852/04 and EC Reg. 183/05, together with the regulations on controlled and integrated production (IFS, AIB, BRC Standards) and voluntary standards have helped to further limit the use of rodenticide baits in the agro-food chains with particular reference to the production, processing, storage and administration areas.
As these environments are constantly threatened by the presence of Rodents, it is necessary to provide for a Rodent monitoring plan within the self-control plans to allow food operators to intercept their presence before it becomes a problem for the production activity as well as for public health.
The monitoring plan must also include the planned control and prevention actions.
Rodent Capture Systems
The presence of mice in the house or in a company is a problem that can often be caught unprepared: which mice traps to choose? Which ones are really effective? Are there side effects for people and other animals?
In this article we will briefly try to give an overview of the types of rodent traps that can be used and the permitted or most suitable uses.
The systems used for deratization interventions to date basically involve the use of two types of devices:
- Anticoagulant rodenticide dispensing devices or poisoning stations (or bait-stations) containing mouthfuls with active ingredient blocked inside the device to prevent accidental spilling, and therefore potential ingestion by people or non-target animals.
- Catch traps of various sizes and models. The simplest are food-activated adhesive traps that retain the Rodent, which then dies from starvation or dehydration. There are also snap traps similar to small trap traps. Since in some cases these systems are in any case considered as bloody, there are now other traps, which utilize systems with tilting or trapdoors, capable of capturing the specimens still alive, so that they can be removed from the capture site without giving bloody treatment to the animal.
- Other systems, available also on the free market, such as ultrasounds or repellents, have not shown satisfactory results in field conditions, and so far there is no good scientific literature to support their real effectiveness.
As far as rodenticide bait dispensers are concerned, they should always be used with great caution and preferably by suitably trained technical personnel. The use of anticoagulant rodenticides in external areas, as well as in localized areas, must always be properly reported, since, despite all possible precautions, minimal risks related to accidental ingestion by non-target organisms cannot be completely eliminated.