Infection

An infection occurs when pathogens enter an organism and multiply there or trigger a reaction from the body. Possible pathogens include bacteria, viruses, fungi, and parasites.

An infection does not necessarily have to lead to disease. Whether symptoms of illness arise depends, among other things, on the pathogen, its quantity, and the defence mechanisms of the affected animal.

Why are infections relevant for dogs?

Dogs can come into contact with numerous pathogens in everyday life. Possible transmission routes include direct contact with other animals, contaminated objects or surfaces, contaminated water or food, as well as transmission by vectors such as ticks and other parasites.

However, contact with a pathogen does not automatically lead to an infection or illness. The immune system can ward off many pathogens before they cause disease.

The risk of a severe course depends, among other things, on the specific pathogen, the age and health status of the dog, as well as its immune status. Puppies and dogs with certain pre-existing conditions or a weakened immune defence are particularly at risk for individual infections.

What distinguishes an infection from other conditions?

An infection is caused by a biological pathogen. These include:

• Bacteria, which multiply in the body and can partially form harmful metabolic products
• Viruses, which rely on host cells for replication
• Fungi, which can infect skin, mucous membranes or internal organs
• Parasites, including for example worms, protozoa and certain arthropods

An infection must be distinguished from a non-infectious disease. An allergy, for example, arises from a misguided or excessive immune reaction to certain substances. In the case of poisoning, the organism is damaged by toxins.

However, infections can also trigger inflammatory reactions. Fever, redness, swelling, pain, or altered blood values are therefore possible accompanying symptoms of an infection, but not definitive proof of a specific cause.

Not every infection causes visible symptoms. Some infections proceed without clinical signs of disease, while others can lead to severe or life-threatening illnesses.

How are infections treated?

Treatment depends on the pathogen, the affected organ system, and the severity of the illness.

Bacterial infections can be treated with antibiotics, provided that their use is medically indicated. However, not every bacterial infection requires antibiotics, and the choice of active ingredient should be based on the suspected or proven susceptibility of the pathogen.

Viral infections can be treated differently depending on the pathogen. For many viral infections, supportive treatment is in the foreground. However, specific antiviral medications are available for individual viral diseases.

Fungal infections are treated with suitable antifungals depending on the type and extent of the infestation. Treatment can take a long time, particularly in deep or chronic infections.

In the case of parasitic infections, different antiparasitic active ingredients are used depending on the pathogen.

Additionally, fluid therapy, painkillers, nutritional support, or further measures may be required. Therefore, the treatment of an infection should not be based solely on the suspected group of pathogens.

When can an infection become dangerous?

The severity of an infection can vary greatly. It becomes problematic particularly when the pathogen spreads in the body, vital organs are affected, or a severe systemic inflammatory reaction occurs.

Signs of a possibly severe illness include, among others:

• pronounced weakness or apathy
• dyspnoea or significantly impaired breathing
• collapse or disturbances of consciousness
• very pale, bluish or unusually discoloured mucous membranes
• repeated vomiting or severe diarrhoea
• significant dehydration
• persistently high body temperature or hypothermia
• severe pain
• refusal of food or water intake

However, body temperature alone does not allow for a reliable assessment of the severity. Even in severe infections, only non-specific symptoms may occur initially.

An example is leptospirosis. The infection caused by Leptospira bacteria can affect the kidneys and liver, among other things, and lead to severe systemic diseases.

Therefore, a veterinary examination should be carried out in the event of clear or increasing signs of illness. Early clarification is particularly important for young, old, or already ill dogs.

How are infections diagnosed?

Which examinations are necessary depends on the suspected pathogen and the affected organ system.

In addition to the clinical examination, for example, the following are used:

• blood tests
• urine or faecal examinations
• swabs and other samples from affected body areas
• microscopic examinations
• pathogen cultures
• PCR tests to detect genetic pathogen material
• serological examinations to detect antibodies or antigens
• imaging techniques in case of involvement of internal organs

A positive test result must always be assessed in conjunction with the clinical symptoms and the respective test method. Depending on the pathogen, healthy animals can also test positive temporarily or permanently without currently being ill.

How can infections be prevented?

The risk of infection cannot be completely avoided. However, various measures can reduce it.

These include in particular:

• appropriate vaccinations against preventable infectious diseases
• effective tick and parasite protection
• Good hygiene with food and water bowls
• Avoidance of obviously contaminated water and food
• Hygienic handling of faeces and excretions
• Cleaning and disinfection in case of certain contagious diseases
• Avoidance of unnecessary contact with acutely ill animals

Which vaccinations and parasite prophylaxes are sensible depends, among other things, on the age, health status, living environment, and individual infection risk of the dog.

A balanced nutrition, an appropriate body weight, and sufficient rest also contribute to general health. However, they do not replace specific measures such as vaccinations or parasite prophylaxis and offer no direct protection against individual pathogens.

Additional hygiene measures are required for infectious diseases that can be transmitted to humans or other animals.