If there is one thing that concerns a farmer most, it is animal health. Healthy cows produce optimally and justify the hefty investment associated with dairy farming. Diagnosing animal diseases becomes a key component of farm management.
In this article, we are going to look at some of the very common diseases at the farm, how to diagnose and manage them for better performance at the farm.
First, we should define some of the important terms we are going to be using throughout this post.
Definition of important terms
Zoonotic disease: – disease that can be transmitted between man and animal.
Food-borne disease: – disease that is transmitted through food. It is a public health concern.
Health: – a state of freedom from any disease or abnormality.
Disease: – Any deviation from a healthy condition. Usually manifested as an inability to perform physiological function at normal levels even when nutritional and environmental requirements are adequate.
WARNING! Always consult a professional if you are unsure of what you are doing.
When diagnosing a disease, you can do it on an individual animal or collectively on a herd/flock.
There are several ways this can be done. We will look at three approaches that are commonly used.
Here, you check for the general appearance of the animal. For instance;
Check close parameters that usually have immediate impact when the animal is unwell. For instance;
Clinical examinations are more advanced hence require expertise. Before you start the process, ensure that you retrain the animal properly to avoid injuries. You should also have the personal protective gear suitable for the job.
The aspects of interest in clinical examination include:
History is critical because it gives a clue as to what disease is suspected. It should be precise and accurate, preferably recorded.
What to consider when gathering an animal’s health history:
Both internal and external environmental factors have a significant impact on the health of the animal.
Outdoor environmental factors include topography, soil type (affects mineral balance) stocking rate (may induce cannibalism), type of pastures (some plants may cause poisoning), etc.
Internal environmental factors include the type of housing, level of sanitation, lighting, ventilation, etc.
Conduct a general inspection of the general appearance of the animal before you know where to settle on.
Do a detailed close examination of the animal while making sure not to upset the animal in any way.
Unsettled animal may not reveal the true conditions because the pulse (or even the body temperature) will increase.
We have seen the many ways you can use to conduct animal health diagnosis. We will now see how to approach a sick animal for examination.
The head is a very important region in an animal. You can use it to check for the animal’s demeanor and facial expression (fright or excitation).
You can also check the head for symmetry and configuration of the mandibles. Use this to check how the animal carries its head.
In the head, you can check if the animal has protruded eyes, which can indicate a problem with the nervous system. Check for spasms, excessive blinking, lacrimation (tear production), etc.
Check the nostrils for excessive discharge of mucus or excessive dilation.
Observe the mucus membranes in the mouth for colour change, erosion of the gums, and salivation.
Check the jugular vein if it is glandular or smooth. Observe its pulse and check if there is any sign of fluid accumulation, which may show a problem with the circulatory system.
Check the size and variations of the lymph nodes. Irregular variation could indicate that the animal is suffering from goiter.
Check the ribcage and observe the rate, strength, and intensity of respiration.
Check the size, alignment/symmetry, and any distention in the abdominal region. Such protrusions may indicate presence of gas/fluid accumulation or tumor.
You should give the udder special attention. Check for symmetry, irregular nodules/swellings, wounds, and dirt. Strip the teat and check the secretions for mastitis.
Check the vulva and the mucus membranes for any deviation in color. Palpate these regions (including the testicles) for any irregular swellings/tumors.
Check discharges from these regions for any abnormality.
Check the animal’s posture and gait. Check for swellings or wounds on the skin.
Check the nose and the ribcage for any abnormality we have discussed in prior.
Start from the mouth and go through the animal in the abdomen, the stomachs, the rectum and the external genitalia.
Here, check the mucus membranes for their colour, the jugular vein for pulse, and the lateral sternum on the left side of the animal to feel the heartbeat.
Skin is the largest organ of the body and the barrier between internal organs and the external environment. Check for wounds, swellings, pests, alopecia, etc.
Check the animal’s conformation and posture. Check for broken limbs as well. Ensure the hooves are well trimmed.
Tentative diagnosis is a temporary diagnosis made by an animal health professional based on the preliminary evaluation of an animal's symptoms, medical history, and physical examination. It is important because it helps guide further diagnostic tests, monitoring, and treatments while waiting for confirmatory test results.
Tentative diagnosis is one that will lead you to identifying the specific problem with your animal. After carrying out the general diagnoses we have covered so far, you can complement them with the following techniques to isolate the case:
Involves direct feeling with the hands/fingers for the size of a swelling, consistency (whether soft or hard), and sensitivity (to pain and temperature).
Strike the body surface to set the deep parts into vibration. These vibrations will emit audible sound, which you can use to tell if the animal is sick or not.
This technique combines both palpation and percussion. It is a useful technique for diagnosing pregnancy in small animals.
Involves listening to sounds produced by the organs. You can listen directly by placing your ear above the surface or by use of a stethoscope.
Set the organs in motion and listen to the sounds they produce.
The health of the animal affects its temperature. Temperature could be normal, high, or low. These deviations could be defines as follows:
Determines the heartbeat rate of the animal. For large animals, you can detect this at the mid-coccidial artery (in the tail end). Use fumeral artery for small animals. You may notice the following from this examination:
Tachycardia - marked increase in pulse rate e.g. during septicaemia or toxaemia. It could also happen during circulatory failure, extreme pain or excitement.
Bradycardia – marked decrease in pulse rate, which occurs mainly on space-occupying lesions in the brain or diaphragm.
Useful for pregnancy diagnosis and deformities in organs.
You can listen to abdominal movements in animals with digestive problems.
Take samples for lab examination. Ensure you follow the good sampling practices.
The samples include:
Use a dry sterile needle and syringe to collect the blood sample. If you are looking for large samples, use the jugular vein to draw the sample.
You can also use coccidial veins or the veins on the tip of the ears to draw samples.
Types of blood samples used for lab analysis
Use a clean and sterile universal bottle to collect the sample. You can use the urine for urinalysis, sugar content, and culture for microbiological analysis.
You can use the faeces for identifying worm infections and for cultural isolation to identify bacterial infections.
Pick a prescapular or parotid lymph node biopsy in a clean dry bottle. You can use the sample for smears and bacterial isolation.
Scape deep into the skin using a clean scalpel and collect in a clean container for ecto-parasite and fungal analysis.
Could be milk or pus. Collect in a clean sampling bottle for chemical or biological analysis.
Take a section of the organ to check for abnormalities like tumors.
You can also collect samples from the feeds, organs, chemicals, plants, content of the stomach, etc.
Specific manifestations of a disease will lead to differential diagnosis to eliminate diseases showing different pathognomonic signs (i.e. signs that cannot be mistaken for any other disease).
Basically, there are three causes of diseases, namely:
They are either extrinsic or intrinsic factors. They include feeding, housing, hygiene, milking techniques, stress, as well as hereditary factors.
These result from physical injuries, chemicals and irradiation.
Primary invaders of the body attack the host and causes diseases. Secondary invaders cause opportunistic infections while a viral infection becomes a predisposing factor for other opportunistic infections.
Inapparent infection happens when the cause of the disease is not manifested in the body. It is also known as sub-clinical or latent infection and the host is a carrier.
There are different types of disease carriers, e.g.
Involves movement of disease-causing microorganism from one (sick) animal to the next.
Diseases that spread through contact are contagious. They can spread through direct contact (e.g. anthrax) or indirect contact when an infectious material gets on an auxiliary body such as feeds or posts then another animal picks it up (e.g. Salmonellosis and Colibacillosis).
Equipment with sharp or piercing edges used for vaccination and intravenous transfusion. Anthrax spreads through this method quite easily.
Vectors may also transmit diseases mechanically and is very common with viral infections.
Usually done for academic and research purposes. The inoculum form one animal is introduced into the other animal to check its effects.
The animal ingests the host through the mouth while feeding or drinking.
The animal inhales the airborne vectors. This is common in anthrax, spore producing bacteria, and fungi.
Infectious materials get into the animal through contact with the mucus membrane. Viruses are very notorious for this.
An infectious agent is introduced into the body via a puncture on the skin. The agents get into the animal through the puncture.
This is the route introduced during medical operations like surgery, dehorning, castration. If the process is not aseptic then the disease takes advantage of it. (See definition of iatrogenic transmission here).
Prophylactic drugs may also cause infection if they are already contaminated before administration.
Common route for STDs in animals. Common in herds with natural breeding systems.
Maintenance of an infection is done for the purpose of propagating the infectious agent. It is achieved through two major processes namely:
They exit one host to another one before they are eradicated. Transmission can either be:
In some cases, the agent cannot exit from their host into another. The host is referred to as a Dead End Host. This breaks the maintenance of the host e.g. Rabies in cattle.
Disease transmission refers to how an infectious disease is spread from one individual to another. In animals, diseases can be transmitted through direct contact (e.g. skin-to-skin), ingestion of contaminated food or water, or via various vectors (e.g. ticks, mosquitoes).
In the case of zoonotic diseases, which are diseases that can be transmitted between animals and humans, the transmission route can be similar, such as direct contact with an infected animal, or through consumption of contaminated food products. It's important to be aware of disease transmission patterns in order to take preventative measures to reduce the spread of disease.
Having discussed how to conduct tentative diagnosis in animals, here are some of the factors affecting disease transmission:
A strong host prevents disease than a weak one.
Include the following:
These factors are influenced by the immunity of the host.
The body has two lines of defense mechanisms namely:
Intact skin bars all microorganisms from the inner organs. There are a number of fatty acids on the skin that inactivates a number of microorganisms.
Sweat and other skin secretions have chemicals that do not allow multiplication of microorganisms.
Any disease-causing agent needs a break on the surface of the skin to gain entry to the organs under the skin.
Normal desquamation sheds off the microorganisms from the skin. Other secretions such as pus also dislodge microorganisms from the host.
Contains cilia that trap big particles e.g. dust. The host then sneezes them out with the microorganism.
Goblet cells in the respiratory tract also produces mucus that trap microorganisms that are released through coughing.
Failure of these actions will lead to infection of the host due to weakening of the immune system.
Infection can also occur when the microorganism develops a special receptor site that they use to attach themselves on the cells.
The mouth produces saliva in large amounts, which dilutes whatever gets through the mouth. The saliva contains lysozyme, which deters microbial growth.
The GIT has an acidic pH, which is not conducive to microbial growth.
Mucus traps the disease-causing microorganism.
Peristalsis makes it hard for any organism to attach, penetrate, and cause diseases.
Most organisms in the GIT majorly exit the body through the faeces and mouth secretions.
Urine is sterile and keeps flushing and diluting the microorganisms. The anatomy of the urinary tract is long making it hard for the microorganism to reach the inner organs for the males.
The female system is shorter and more exposed making it easy for the microorganisms to access and cause infection. It has a pH of 5.0, which is acidic hence deters growth of microorganisms.
The udder hormone (oestrogen) also suppresses microbial growth.
STDs are introduced through coitus. They are expelled through urine (e.g. leptospirosis) and genital secretions.
The eye has tear gland, which produces tears that wash the conjunctiva. The tears also contain enzymes that digest microbes. It also has eyelids that sweep the eye membrane periodically and involuntarily to keep the eye safe and clean.
Sometimes, microbes in the blood get to the eyes and cause infection on the eye membrane (systemic infection).
Immunity is the lack of susceptibility to infection or disease on the part of the host. Immunity can be either natural or acquired.
The host is naturally immune to a particular disease or infection (e.g. zebu have naturally high immunity to anthrax).
Natural immunity can be specific to an individual or a particular species.
It may also be influenced by other factors such as age, heredity, nutrition, and environment.
Can be divided into two types:
Involves the cells themselves and is more important in humans than in animals.
Once the body is under attack, the cells undergo alterations and acquire phagocytic ability.
Can be either active or passive.
An animal can acquire this type of immunity through recovery from a disease as a result of antigen-antibody reactions. Creation of antibodies prevents the animal from getting this disease.
It can also be acquired through vaccination. An attenuated/less-virulent form of the agent is introduced into the target animal to reduce virulence when the real diseases agent attacks the body.
After the introduction of the agent through vaccination, traces remain in the system and continue to produce the antibodies in the system of the host. This is termed as pre-immunity.
In other cases, the agent of the disease-causing microorganism is completely wiped off the system after complete recovery. This is termed as sterile immunity.
This is the immunity that is passively passed from one animal to the next. It is usually short term (3 -6 months) when compared to active immunity, which can be lifelong.
Disease control is done with the major aim of ensuring that the animals are healthy so that they can produce and reproduce.
Different governments have measures in place to ensure that animal diseases are controlled to manageable levels.
To prevent occurrence, there should be early detection, diagnosis, and treatment for the diseases e.g. mastitis and helminthiasis. They should be frequently checked.
Infer immunity to all animals by ensuring that:
Ensure the infection is contained to prevent spreading through the herd. You can achieve this by:
Ensure there is minimal contact with the animals and animal products
Maintain high standards of hygiene.
Destruction is a control method that eliminates the host and the microbe. It has been used to control foot and mouth disease.
Public awareness through mass education is particularly important in containing foodborne and zoonotic diseases.
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