Mice and rats

Fight ‘continues’ in mice and rats. Difficult and complex because of their characteristics, it is necessary to take decisive action to prevent sanitary problems

Stefano Scarponi 

To the same family of wild mice, MURIDAE, but of most hygienic-sanitary interest, are mice (Mus musculus) and rats (Rattus norvegicus and Rattus rattus) belong. They have slender bodies, scaly tail almost devoid of hair and almost long like the body or more for the black rat of roof).


The domestic mouse
It’s a rodent now famous and it’s called by almost all pest control operators with his linneian name. The Mus musculus is an infesting entity that can colonize each site, from the washing machine at home (where the instinct it preserves the undeniable risks of moving parts: this is the rotating basket of laundry during centrifugation!) to high technology data processing centres where its potential site is seen as a real disaster. More frequently found in the food chain where it can be defined as an endemic entity, with alarming epidemic events.
The “our” little mouse up to 30 g in weight, but it is a good eater: three to five grams per day (proportion of a man weighing 70 kg should eat 7 to over 10 kg of food per day), in return it drinks little (1 to 2 cc. / day) but it can live without water for long periods.
It produces 1.2 cc of urine per day with 2 g of feces scattered in small “bolus” that the animal lays with a constant frequency throughout the period of his activity which is typically during the and the night.

At its justification also the feeding is diluted in 10-15 snacks (from two hundred to five hundred milligrams per ingestion). In fact the latter datum should not be placed in brackets because it represents a characteristics to be taken into account in the fight’s program: in front of a taster of this force you must dispose of firearms and appropriate application techniques.
The bio-ethological data most important are: duration of life in conditions of captivity for up to four years, life’s expectancy (in natural conditions) estimated at about 6 months.
The sexual maturity is at two and a half months since birth and it has 20 days of gestation; the number of broods are in a year per female 6-10 for fifty babies! The psycho-physical characteristics of these muridae can be summarized in a considerable curiosity mitigated by fear, however justified, with not obvious phenomena neophobia (fear of new). Furthermore, they present exceptional performance: they can jump up to 30 cm, they throw from heights without damage in excess of 2 m, they pass in little holes larger than one centimetre in diameter and they are capable of climbing on each surface: the mini tightrope walkers athletes. Of these highly invasive characteristics is necessary to take into account in evaluations of rat-proofing.

Technical application

The struggle against mice often end with their victory, or because these entities are infesting entity equipped, as we have seen, with optimum mental and physical characteristics, but also with a remarkable resistance to physiological substances that are most commonly used as a rodenticide. This greatly complicate the realization interventions to fight because in some cases are used bait whose active ingredient is “active” against rats, less or not at all against the small rodents.
The approach of the fight that (except for rare exceptions) takes place in confined spaces is based on the general evaluation of the environment in which they will be operating. The treatment area must be divided into infested areas, area at risk and it is equally important to identify the pressure of infestation or the ways in which it is likely to assume the arrival of the “settlers” by the sharp teeth.
After the monitoring of the area of intervention, you have to identify the “modus operandi”, which generally consists in the intervention at preventive-maintenance level: sealing passages, put in place networks and dams and eliminate areas of refuge (this step can be performed prior or after the placement of bait).
After to have laid the basis for the positioning of the bait, you need to define their number and their locations. Each point bait so identified must be defined in the type of bait (food and basic pa), quantity of bait and type of protection best suited to the needs.
In some cases of particular difficulty can be useful to undertake a treatment of pasture (pre-baiting) with the use of placebo (no active bait with no pa); which with the intention to evaluate the extent of infestation, the dietary habits and / or induce them to practice that will be used. A kind of rehearsal, evocative of the text, often cited in scholarly literature, but very little used in practice common: as all the technical possibilities can
be effective to the extent that it is used where the really necessary, and a further case for the applicability of the pasture is to accustom the mice to areas of little or no interacting with the activities conducted at sites of murine reclamation. Once the bait’s items are placed they must be restored and adapted as the needs that are created.
Completed the phase of reclamation is often useful to perform a finishing maintenance, since it considers necessity, but it is important to the critical scrutiny of these treatments.
After this you have to plan the timing of interventions with the aim of maintaining the results obtained, gradually improving and consolidating the same time preventing the risk of re-infestation with interventions against the invasions, with careful monitoring inspection, with the evaluation of suppliers, and, not insignificant, with the improvement of our knowledge and skills in the context of the too often neglected field of environmental hygiene.
This is true even if the intervention is aimed at assessing a contracted service, it must be remembered that the Law on occupational safety refers to the risk of hygiene and the need to eliminate or at least minimize the risk of what you want nature, origin. At professional level everything must or should be certified on forms to assess the results at every stage of intervention and for all period of time where the timing is expressed. This phase is common to all the remediation of any infesting species will be investigated further in a separate

The black rat of the roofs

This species has come into our areas from the far Mesopotamia, probably taking advantage of trades Maritime achieved with Trireme of the Roman Empire. It’s certainly the most important cause of outbreaks of plague during the Middle Ages and even today it is a potential vector of many diseases: salmonella, epizootic aphtas , adenovirus, leptospirosis, listeriosis, rickettsia, arborvirus, dermatofitosis, leishmaniasis, verminiosis and others.
Most agile of the fort rat of sewer, normally it colonizes the high floors of the structures and silos often the crown of the trees, with a certain fondness for the pine trees and palms.
Males of the species can reach 300/500 g of weight, body length can reach 16-21cm, while the tail is longer than the body of at least a couple of centimetres. The ears are rather long and usually succeed, folded to cover the eye.
The diet is omnivorous, with preference to the proteins of plant origin and a daily reach more than 20 g dry matter and 20 ml of water, but the black rat of roof can remain without drinking for several days.
Excrements and urines are only slightly less than the amount ingested.
The duration of life in captivity can reach six years, while in nature typically can not exceed one year. It reaches the sexual maturity after two and a half months after the birth, the gestation period is three weeks, the weaning of four. The broods per female in one year are between six and eight for a number of births of 34 subjects. In this case the neophobia is especially strong in populations established by a certain time and then by consolidated habits.
The psycho-physical characteristics make it an able climber (able to climb vertical pipes within 10 cm diameter, to the point that may appear in the cup of the bathrooms and mysteriously disappear), a good jumper and a moderate swimmer.
Technical application

Having to deal in the fight against Rattus rattus you must take account of this neophobia of this species and then each reclamation action is good that it sent eradication occurred.
The treatments are set with some methodological similarities already discussed in chapter: identification of contaminated sites and areas at risk and the possible routes of infestation.
These sites are recognizable by the presence of grease (betalanolin), faeces, growing, paths, and dens or “nests”.
Localized infestation you switch the positioning of points of an appropriate number of bait and bait suitable for food type. Even in this case it may be useful to the technique of pasture with placebo. The timing of treatments generally involves inspection / applications on a monthly basis and careful anti-invading interventions that must always take into account of the agility and climbing ability of this species. Attention then to pipes, wires, poles, and so allow our funambulist rat of “access”, including the walls not perfectly smooth.
Even in this case is a good idea in the professional assistance to formalize the data on treatments with precise and detailed certification.

The norway rat or rat of the sewer

In little more than a century, from the Russian steppes, the species has conquered almost the entire planet. During the second half of the eighteenth century, probably due to a telluric phenomenon of large-scale the immigration begins that in a few decades allows him to invade Europe and later with the commercial trades reaches the Americas and so on the other continents. Vigorous and aggressive animal it detracts space to Rattus rattus, and in short time it occupies the subterranean habitats, especially if connected to the water or drainage system.

The males can overcome the weight of 600 g with dimensions similar to rats of roof, but with more squatter body, shorter tail of the body and ears and eyes smaller. In the laboratory it comes to living up to 7 years, but in nature, life expectancy hardly reaches 10/11 months.
It reaches the sexual maturity between two and a half months and three months. The gestation period is just over three weeks and the weaning of four. A female in a year is capable of producing a child of 40 units in 4-5 broods.
The solid diet is omnivore, with some preference for animal protein by up to 10% of body weight with a water contribution a little lower; urine and faeces in proportion.
The psycho-physical sensorial characteristics indicate animals with sense of smell, taste, touch-hearing very developed; but they can rely on a rather limited view.
They are very strong, able to jump on top of almost 80 cm and in the long jump (stationary) of 10/20 cm above the meter, and with leapfrogging doubled the performance; they are able to swim to the surface and in apnoea; they can dig long tunnels into the ground drilling thin cement barricades and tender metal.

Technical application

Most of what has been said for the previous case it is applicable to the Norway rat (see neophobia of black rat); for this reason it’s good then try to leave everything as is, intervening with practices of rat-proofing and maintenance only after the stage of eradication. For the large-scale interventions the procedure should (if possible) to follow a centripetal pattern, with health barriers that prevent to almost isolated and alarmed individuals to migrate to other sites, disseminating micro infestations capable in a short time to established for the high reproductive capacity of species. Particular attention should be placed to protect the bait because the habitat of these rodents often coincides with to non-target animals and, in many cases with that of man.

Planning and calendar of treatment

It is a good rule to follow the objective to eliminate the problem as quickly as possible, it is not rational reduce the infestation never get to solve the problem in a conclusively way.
This usually involves a massive intervent in two or three phases. And here the most difficult and impostant step: the maintenance of the results.
Why difficult?
Overall because ceased especially the emergency phase you are likely to decrease attention to the problem and also because the few remaining specimens tend to avoid routine monitoring, requiring more inspecting effort.

Complementary treatments

The complementary treatments are fundamental because they have the basic objective of making difficult the re-infestation and they become in the future projections a sort of “prevention”. The anti-invasion treatments involve the affix of barriers and nets a rat proof.
It is very important at this stage to analyze the closure systems (photocells or with automatic closing doors) adequated to specific needs, particularly in industrial or hospital.
For the territory it would be well to pay attention to the drainage system, the watersheds, and agricultural farms.
This chapter is well positioned in the context of land reclamation and / or engineering “sanitation”.

Forms – Detection plans
This aspect of the murine reclamation is part of the information’s management.
The data collected in paper or electronic terms allow to measure and evaluate the results, with consequent optimization of future treatments.
It seems natural to each one of us who are playing cards to rearrange the cards second appropriate patterns to the game: for instance all the seeds of squares on one side and well-sorted from the lowest to highest. The chances of winning are based on the ease of check cards and this is facilitated by the fact to see them sequentially before our eyes: the disorder would make easy the mistake.