Sources of Disease
When controlling disease it is important to keep in mind that anything can be a potential risk. Diseases can be infectious or non-infectious. Below are some examples of potential risks of disease in a rodent facility.
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Nutrition: An unbalanced diet can be a source of disease as the animals can get sick very easily if they don’t get all the nutrients they need. A balanced diet will include water, carbohydrate, proteins, fats, vitamins and minerals. How the diet is stored is also essential to avoid diseases in an animal facility. If diet is not stored correctly, wild rodents, insects and pests can reach the diet and will contaminate the food and spread disease. If the diet is too old it will lose nutrients and won’t be beneficial to the animal’s health. Water: needs to be clean and pure to avoid any type of contamination to the animals.
Environment: uncontrolled environment as noise, light, temperature and humidity can cause stress in the animals which will low their immune system causing sickness and making them more vulnerable for diseases. Social animals should have companies
Hygiene: clean environment result in fewer bacteria around, clean gloves and scrubs help to prevent cross contamination from human to the animal or from one animal to others. Animals should have enough space according to their specie to present their natural behaviour.
Metabolic dysfunction: When an organ of the body stop working in the way it was supposed to, it will causes health and mental problems. Diabetes is one of them. The body will not produce the right amount of insulin. It will be too much or too little. Another example can be Parkinson’s and Alzheimer’s, they are neurodegenerative diseases. Animal with metabolic problems should be monitored very well to see if the problem is stable or if it is getting worse.
Inheritance: Inheritance disease is causes by mutation/alteration of one or more genes. Examples of this disease can be cystic fibrosis, when a thick mucus will be accumulated on lungs and digestive tracks.
Trauma: Can be physical or psychological. Example of trauma can be a close or open wounds, broken part of the body as broken leg, foot, spine, etc. A mental trauma can be a very stressful situation that can involve extreme violence, accident, terrorism, natural disaster etc. It is called posttraumatic disorder (PTSD).
Radiation: When an animal is exposed to high level of radiation it can cause many problems in short and long term. Some of the problems will present within 24 hours, clinical signs of radiation can be vomiting, nausea, death, infection and bleeding. Mice can lose weight, became anaemic, have mobility reduced, become lethargic and have breathe problems, etc. In a long term, the animal or human can develop cancer. Foetus will probably be deformed if exposed to radiation during pregnancy. Radiation in controlled doses can also cure disease. Who are exposed to a low doses of radiation for really long periods of time can develop chronic radiation syndrome.
Chemicals: Can be a source of disease or even lead to death when not used correctly. This substances can be dangers in different ways, some chemicals will be harmful if in touch with the skin, some will be danger if inhaled or when mixed with other substances. Depending which chemical is being used can be toxic and really bad for lungs, eyes, skin and some can even cause deformation in foetus if a pregnant female is exposed to. Heavy metals as mercury can be danger and can damage the brain, kidneys and lungs.
Tumours: When abnormal cells develop very, very fast in the body. Reasons to have tumours can be genetic or environmental. Tumours can be benign or malignant. A benign tumour won’t spread in the body as the malignant will spread to any part of the body very fast and it is called cancer.
Arachnids: Can cause infectious disease. Some spiders are poisonous and others aren’t. The poisonous can even cause death, but they are not common in the UK. Some countries will have more of those spiders than others. In the UK most of spiders have venomous bite, but they don’t kill you. The bites have neurotoxins and insecticides and it can be painful. Bite symptoms can vary from discomfort and numb to swelling.
Bacteria: can cause infectious disease and can be spreaded in different ways. There are more bacteria than cells in the human body. Not all bacteria are bad for the body, some of them are good and needed for a good heath. They can reproduce very fast. Bacteria disease can be spread by saliva, air, skin contact, food and etc. Some examples of diseases caused by bacteria are: Salmonella, tuberculosis, meningitis, leprosies, eye infection and etc. Some diseases can low the immune system and some bacteria can cause death.
Example A to F:
Tapeworm/ Cestodes: They are parasites that live in the intestines of vertebrates animals. A good way to avoid contamination and the spread from these disease is avoid undercook food, especially meat. Always wash hands before eat and after using the toilet. Good hygiene is essential to prevent most diseases. Wash fruits and veggies very well with clean water before eaten them. Avoid places where faeces is not disposable in a safe way.
Pinworm: they live in the rectum and colon. The contamination occurs when people eat their eggs. Can be through food or by the hands. It is important to clean hands after going to the toilet and before eaten. It helps to avoid contamination.
It is very common for kids to have them, and when they get it is easily spread to the rest of the family, as the eggs can attach to nails, clothes, towels and other objects. One of the symptoms can be anal itching.
Ticks are small bugs that survive sucking blood from humans or animals. Their bite can cause Lyme diseases, Rocky Mountain spotted fever and other diseases if the animal is infected. It can be found outdoor, in grass, trees leaves, etc. So when people go for a walk or if animals are playing outside, there is a chance of one of them attach to the animals or to the person and start to feed from them. The way to avoid them is removing the ticks from animals or from the body, there is a tool to help with that and vacuum and clean the house very well, the outside of the house must be kept clean too. Wash clothes and bedding with high temperature water. They can feed from someone that have a disease and it can be transmitted to the next host on the next feeding.
Liver Fluke is a parasite that lives in bile ducts and on the liver of infected animals or humans. This can cause fascioliasis disease and can’t be passed from human to human. Usually contamination happen when people or animals drink water contaminated with liver fluke, when eat freshwater fish contaminated, or when wash veggies and fruits with contaminated water. One way to avoid the spread of the disease is to drink, wash and cook with clean water, and always cook very well fish and other meats.
There is medication to treat the disease. But some people can live for many years without showing any sigh of the disease.
Mites: They are arthropods, there are thousands different species of mites, some of them can cause allergies, rash in the skin and other problems. The best way to prevent them at home is keeping everything clean, always hoover the house, wash cloths, towels and bedding with hot water.
Houseflies: They feed from contaminated places as faeces and bins and the pathogens attach to their mouth and legs, and this is how they contaminate food or the surfaces where the foods are. They also poo everywhere, including on food and drinks that people eat. Best way to avoid them is keeping things clean and covered. Inside and outside of the house should be kept free from flies and a clean environment is the best way to keep them away.
Tapeworm: They are parasites that live in the intestines of vertebrates animals. They don’t have digestive system and they absorb nutrients when the food pass by them. Their body is actually an amount of proglottids that contains male and female reproductive system. Their eggs can be found in the grass, veggies, fruits, etc., and their eggs can survive for long periods of time. Pigs and cows are infected when they eat from those contaminated places. In the animal intestines, the eggs hatch. And cover the intestine wall and after move to the muscle and become cysticerci. It can live for years in the animal body. Humans are infected when they eat raw meat that is contaminated and/or meat that is not cooked correctly. In about 2 months the cysticercus living in the human body will grow into an adult tapeworm, and they can be as big as 5 metres.
When the proglottis is eliminated with faeces it will contaminated the soil, water, grass and the pig, caw or other animals will eat from these places and will be infected. Then the cycle start again.
Ticks: They have 4 stages, first they are eggs, after they became a larvae of 6 legs, a case worm of 8 legs and then an adult. When they hatch they have to feed on blood to keep alive and growing in all stages. They can live for 2 or 3 years depending on their species. They can feed from mammals, reptiles, amphibious and birds. Sometimes the animals or human won’t even notice that there is a tick feeding from their body, this happens because in their saliva contain anaesthetic that will make the feeding being painless. They can feed for several days from the same source and then drop on the floor and when they need to feed again they found a new host. As an adult, their purpose is to reproduce. Females can lay thousands of eggs.
Learning Outcome 2: “Evaluate methods for minimising the risks from potential disease organisms”
2.1 Briefly describe how the risks from disease organisms are minimised in the animal facility
2.2 Apply suitable disease control methods for two of the potential sources of disease from the answers to 1.1, dependant on age, scientific use etc.
It is very important to control disease in an animal facility because it can affect the health of the animals and also the experiments results. Below it will explained how to minimise risk of diseases in a facility with mice.
Animals held for scientific procedures must be monitored every single day. This is the law, according to the Home Office Code of practice.
Animals must be checked individually for signs of disease and if necessary examination post mortem needs to be done if animal is found dead under suspicion reason. There are many types of diseases and some of them can be avoided with simple measurements such as good husbandry.
As mentioned before, anything can be a potential risk of disease: diet, environment, injuries, poor handling, and contact with people are a few examples.
Good husbandry can reduce and/or maybe avoid diseases in the unit and good nutrition will improve their immunology system helping to prevent sickness and disease.
Barriers are another method of controlling and minimizing risks of contamination. They are made to prevent the entry of micro and macro organisms into the animal facility.There are many different types of barriers and to choose the best method it is necessary to determine the kind of unwanted things/organisms that need to stay away from the animals and the facility. Barriers exist to protect the animals against micro-organisms and also to protect people that are working with animals. Doors, step-over barriers, ventilation pressure in the rooms, cleanliness are examples of barriers that will help against disease.
To avoid bringing any kind of unwanted organisms into the facility, staff must change their clothes and shoes. When entering an animal unit the Personal Protective Equipment (PPE) must be worn all the time and the type of equipment to be worn depends on the type of the facility. With rodents the PPE will mostly be gloves, gown/scrub, oversleeves, overshoes or appropriate shoes, mask and goggles when using chemicals. Staff wearing a scrub suit helps prevent live organisms from entering or leaving the facility. Gloves must be worn all the time and this helps prevent contamination from people to the animal and from animals to people (e.g. If mice urinate on the hands when being handled contamination will be avoided if gloves are in place and changed accordingly). Incorrect use or lack of using PPE can result in diseases being spread.
Gloves and overshoes.
Safety glasses Masks.
(Photos above are from JR unit).
The air in the facility must be filtered to avoid any microorganisms. The IVC (Individually Ventilated Cage) is where rodents live and they have an individual air intake which prevents cross-contamination between animals living close to each other. This is a way of preventing disease to spread around the unit. The IVC use HEPA-filters (High Efficiency-Particulate Air), which will protect them against those organisms.
Change station equipment must be used correctly. E.g. Needs to be switched on as it draws the airflow from an opened cage protecting the animal environment and the user from allergens, if it is not turned on then either the animals or staff are not protected. It will lower the risks of air born infections and will be beneficial for the animals and also for technicians and researchers working with rodents. To help staff and researchers in the unit, there are SOPs (Standard Operating Procedures) and Risk assessments in all areas.
Zoonotic disease for example can be passed to humans and can spread to healthy animals.-hopefully correct use of barriers like PPE and change stations can prevent this.
It is important to clean the change station after each use and all equipment used in the facility must be disinfected to minimise disease through cross contamination. To avoid cross contamination between cages gloves must be changed when dealing with different animals and Anistel (disinfectant) must be sprayed on the gloves to kill any bacteria that may be present in between cage changing.
Autoclaving is a very important step against diseases and bacteria, it is part of the barrier system because will sterilize bedding, cages, tubes, bottles and almost everything related to their cages. Sterilization of all items that will be in contact direct or not with the animals will minimize risks of contamination.
Animals from unknown sources can spread disease so places where animals are supplied from should be safe and trusted suppliers should be used whenever possible. It is essential to know about the place of origin of animals and any disease that any specific strain is more vulnerable to catch. When possible it is better to breed animals in your own facility if there is permission for that from the Home Office. Breeding units in the facility are safer.
When working in big units it is possible to go from one wing to another without risking contamination, but when moving between some of these wings it will be necessary to wait several hours to be allowed to enter the other wing.
Some places have different wings because of the different organisms present in each wing. To control the spread of organisms, all people that enter a dirty area should not enter a clean area. The other way around is possible because wouldn’t cause any risk. Equipment used in the wings can’t be moved around unless is sterilized. Even gowns and scrubs should be cleaned inside the wing that they were used, avoiding cross contamination. To avoid cross contamination staff should be trained and made aware and other personnel allowed restricted card access to minimize risk.
New animals should go to quarantine. If they are free from excluded diseases, they can be introduced to the appropriate wing. If they present any type of disease, the NACWO (Named Animal Care and Welfare Officer) will be informed and the NVS (Named Veterinary Surgeon) will be contacted to check if treatment is possible and the researcher informed of available options. If yes, then the animal will be treated and then screened again, if the results are good the animal will be kept and sent to the unit.
Close attention to details and responsibility are essential to avoid spreading diseases. Everyone needs to be committed to minimize the risks, because a simple mistake can cause real damage and animal lives will be in danger and years of research can be lost.
All barriers are in place and everyone should adhere to them because this reduces the risk of cross contamination throughout a facility. Most importantly those that need access should be the only ones that have it.
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Nutrition: One of the reason that animals get sick is bad nutrition. An unbalanced diet can be a source of disease as the animals can get sick very easily if they don’t get all the nutrients they need. It all start since they are born. If they are not fed properly, they won’t grow as expected and they will become weak and sick. Bad nutrition can have a big impact on the experiments. For example, if an animals is being tested for a new medication, there is a big chance that the medication will not work how it should if the animal is underweight, weak or with other health problems. Health animals will recover better from surgery and if they are well-nourished they will respond better to treatments. Mice that have access to good nutrition will reproduce better, having healthier litters. Unbalanced diet can cause diabetes, obesity, hair loss, weight loss, etc. A balanced diet will include clean water, carbohydrate, proteins, fats, vitamins and minerals. Deficiency in vitamin B for example, can be bad for memory and increase chances of having Alzheimer’s or other cognitive impairment. Lack of vitamin A can increase myeloid cells in bone marrow, spleen, and peripheral blood. Excess of protein can cause renal problems. The excess or lack of any nutrients can cause serious diseases. How the diet is stored is also essential to avoid diseases in an animal facility. If diet is not stored correctly, wild rodents, insects and pests can reach the diet and will contaminate the food and spread disease. If the diet is too old it will lose nutrients and won’t be beneficial to the animal’s health. Food should be stored on pallets to allow circulation of air. Water: needs to be clean and pure to avoid any type of contamination to the animals. RO water (Reverse Osmosis, process of purification of the water) is a good option to avoid diseases. Animals should have a good portion of food so they won’t lose weight for eating too little or get obese for eating too much (depends on the specie). According to the Home Office HO and Code of Practice mice must have free access all the time to food of good quality and clean water. Water must be changed regularly and must be free from contamination, if they don’t have access to enough water they can dehydrated very fast and die.
Environment: The animals need to be allowed to express their natural behavior. Mice are naturally social animals, so it is important for them to have company.
Animals should live in clean places, cages where mice live can be cleaned once a week, but if necessary they must be cleaned more often. Over cleaning can cause anxious mice as it also removes most of their natural smells from the cage. It is important to transfer to the new/clean cage some of the bedding from the soiled one.
The cages where mice are held must have a good space for them to move and also have a basket of food and bottle of water. Disrespecting stocking density will cause fighting, stress, high levels of ammonia and would break the law. Single housed animals are not allowed unless it can be justified with the Home Office for a short period of time.
The cage must be comfortable, dry and clean. Every cage should have enough bedding and nesting materials. Enrichment is essential for them to recreate an environment as close to nature as possible and encourages their normal behavior. Mice are prey animals in the wild which means they are naturally hunted – tubes and houses allow them to hide, sizzle nest allows them to build, and chew blocks allow them to gnaw. These simple enrichments will improve their quality of life and reduce stress. Red houses and tubes are provided because mice do not see red, so they feel safe and hidden
(Photos from JR)
Animal room temperature should be around 21°C, with variation of +/- 2. High or low fluctuations in temperature and humidity have bad consequences-see below. Humidity should be around 55% with variation of +/-10.
Rapid heat loss
Dehydration – sweat more
Pups unable to regulate temperature which cause high mortality.
Disease and infection- ringtail
Temperature and humidity should be checked every day .All the parameters used for housing are set by Home Office Code of Practice. Hygrometers are also used in the unit, they are an instrument used for measuring the moisture content in the atmosphere.
Wall thermometer Hand held thermometer Hygrometer
The lighting is also very important because this can affect their breeding, which usually occurs at night. If the lights are not controlled, having too many hours of light or darkness, this would upset the natural rhythm (circadian cycle and life cycle) and cause stress. They have a period of 12 hours light and 12 hours dark. As mice are nocturnal animals they will be more active during this period.
According to the Home Office Code of Practice the intensity of the light must be 350 – 400 lux. For albino mice the intensity should be less than 60 lux, because high intensity can damage their retina. It is a good idea to place cages with albino mice away from the light, keeping them on lower shelves on the rack. IVC cages are tinted yellow, this helps soften the intensity. A photometer is the instrument used to measures light intensity. It is necessary to direct the photometer to the light in the room to measure.
Photometer (google images)
Noise is another factor that needs to be taken into consideration when housing mice. Loud noise can be very stressful for them, so staff and technicians should avoid any unnecessary noise, due to their sensitive hearing. They hear and vocalize in ultrasonic range (above 20 kHz). Sound of coins, dripping taps, and trolley wheels (squeaky) can be very disturbing for them. Checking taps, adding oil to wheels will reduce noise in the room.
Learning Outcome 3: “Know relevant health and safety legislation and practices” Pass, Merit and Distinction Describe how the health and safety of the animals and people is maintained in relation to this assignment
People should work in a safe place and animals should live in a safe environment. To help with that, as mentioned before, there are guides and rules that must be followed for the health and safety of everyone involved.
Some of the guides are: Health and Safety at Work Act 1974, Risk assessments, Code of Practice, Standard Operating Procedures (SOP) and COSHH (Control of Substances Hazardous to Health). They explain about safety and risks (yours and the others),
The Health and Safety at Work Act 1974 says that employers must ensure the health, safety and welfare of all their employees.
Personal protective equipment at work regulations 1992 says that employers have to provide PPE (personal protective equipment) for everyone and it includes clothing and equipment at work and employees have to make sure that they are using it. PPE must be worn all the time when working.
SOPs explain how to do jobs in the unit safely and correctly like how to operate the change station correctly. Risk assessments describe the possible risks in doing activities and how to avoid such risks.
When working with animals, the main PPE will be gloves, gowns, overshoes, over sleeves and mask. It can help prevent contamination, spread of disease and allergies. The main hazards for people are: Allergies, injury and infections. Employers must minimize any risk, so equipment and training must be provided.
Equipment should be checked often to see if they are working properly, they should be calibrated when necessary and only trained people should use them.
Sharp bins must be provided when using syringes or sharp objects.
When using disinfectant like Anistel, bleach or other chemicals, the regulations require that employers control exposure to hazardous substances to prevent ill health (COSHH – Control of Substances Hazardous to Health) and appropriate PPE must be worn. Hazardous substances can be: certain chemicals, bacteria, dust or any substances that can cause health problems. The Health and Safety at Work Act 1974 says employers must ensure the health, safety and welfare of all their employees. Employers must minimize any risks to their staff, training and equipment to improve health and safety must be provided.
To help understand how things work in the unit there are SOPs (Standard Operating Procedure) and Risk assessments. An SOP explains step by step exactly how to do everything that needs to be done in the unit and tells how to do things in a safe way. On the other hand risk assessments describe the possible risks in doing some activities and how to avoid these risks and be safer.
Laboratory Animal Housing and Routines – Janet Buckland
Personal protective Equipment at work regulations 1992
Code of Practice
Health and Safety at Work Act 1974
My own assignments from pre level 3 (Oxford University)
Handbook of Laboratory animal management and welfare – Sarah Wolfensohn and Maggie Lloyd – 1996
Images from my facility and from google images.
The Learning Curve IAT level 3 – Disease control
My own experience
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