Leukocytes

Leukocytes – i.e. white blood cells – are the actual engine of your dog’s immune system. They recognise invaders such as bacteria, viruses or parasites and launch the counter-attack first. In short: without them, your dog would be defenceless.

As a dog owner, you usually come across this term at the vet’s when the blood count suddenly shows abnormal values. What looks like a dry laboratory value at first glance is actually a fairly direct signal: your dog’s immune system is currently fighting – or it is too exhausted to fight.

What happens when leukocytes are too high?

Elevated leukocytes – known in technical terms as leucocytosis – mean that the immune system is running at full capacity. Somewhere in the body, an infection or inflammation is active to which the organism is responding.

The normal range is 6,000 to 17,000 cells per microlitre of blood. If the value is above this, it is worth taking a closer look.

Typical triggers for high values:

• Bacterial infections – for example infected wounds, urinary tract infections or dental problems
• Parasite infestation by worms or fleas
• Joint or intestinal inflammation
• Physical stress after surgery or injuries
• In rarer cases: leukaemia or other cancers

How can I tell that something is wrong with the white blood cells?

You naturally cannot feel the leukocytes themselves – but the underlying illness almost always shows in some way. Dog owners usually first notice that their dog is “just not quite himself” before specific symptoms appear.

Warning signs you should take seriously:

• Persistent tiredness, even though the dog has slept enough
• Recurrent infections – more than two or three times a year
• Wounds that do not close or become inflamed repeatedly
• Gum bleeding or noticeably bad breath
• Diarrhoea or vomiting without an identifiable trigger
• Fever or body temperature above 39 °C

What do low leukocyte values mean?

Below 6,000 leukocytes per microlitre is referred to as leucopenia – the immune system is weakened and the dog can defend itself less effectively against pathogens. This can quickly become dangerous, especially in young or older dogs.

Frequent causes:

• Viral infections such as parvovirus or distemper
• Autoimmune diseases in which the body attacks its own cells
• Bone marrow problems
• Chemotherapy treatments

The different types of white blood cells

How leukocytes are distributed among their subgroups depends on the laboratory and the measurement method. The proportions below are taken from the reference values in the MSD Veterinary Manual. Other laboratories give significantly wider ranges, for example up to 47 per cent for lymphocytes. The range on your laboratory report is binding.

Neutrophils make up the largest group, at 58 to 85 per cent according to the MSD Veterinary Manual. They are, so to speak, the first responders – they migrate to sites of infection first and fight mainly bacteria.

Lymphocytes (8 to 21 per cent) take over targeted defence. They produce antibodies and – what is remarkable – they remember pathogens for future encounters.

Eosinophils (0 to 9 per cent) have specialised in parasites and allergic reactions. Their values can rise sharply in the blood count in cases of worm infestation – an important clue for the vet.

Monocytes (2 to 10 per cent) develop into so-called macrophages, i.e. phagocytic cells that remove tissue debris and dead pathogens.

Basophils (less than 1 per cent) are the rarest group and play a role mainly in allergic reactions.

When should I take my dog to the vet?

Immediately if your dog has a fever above 39.5 °C, is vomiting persistently or appears apathetic and refuses food. Every hour counts here.

You should make an appointment within two to three days if:

• Diarrhoea lasting longer than 24 hours
• Wounds that become red or start to suppurate
• Unusual tiredness without an identifiable cause
• Symptoms that return after apparent recovery

The blood count provides the vet with crucial clues: elevated neutrophils point to bacterial infections, while elevated eosinophils suggest parasites. This distinction is no small matter – it directly determines which treatment is appropriate.

How are leukocyte disorders treated?

Treatment always depends on the cause – not on the blood value itself. The value only shows that something is wrong; what exactly lies behind it must be determined by the vet.

Bacterial infections are treated with targeted antibiotics. Parasites require special deworming treatments or antiparasitics. In autoimmune diseases, corticosteroids can dampen the overactive immune response. Cancers such as leukaemia are usually treated with chemotherapy.

What you can do concretely as an owner: avoid stress as far as possible, pay attention to balanced nutrition, give the dog sufficient rest – and administer the medication on time. This may sound trivial, but it makes a real difference for healing.