Brucellosis

Brucellosis is a bacterial infection that passes to people from farm animals: goats, sheep, cattle, pigs and, less often, dogs. The animals frequently look perfectly healthy, so infection happens without anyone suspecting it — most often through unpasteurised milk and the cheese made from it. What makes the illness treacherous is not its severity but its vagueness: it produces a drawn-out fever, night sweats and aches easily mistaken for flu, for exhaustion or for a back problem. Where milk is pasteurised and herds are monitored, brucellosis is rare; around the Mediterranean, in the Middle East, in Central Asia and in Latin America it still turns up regularly.

How the infection is caught

The main route is food. The bacterium lives in the milk of an infected animal and survives in anything made from that milk without heat: soft farmhouse cheeses, curds, home-fermented milk. Pasteurisation destroys it, and hard cheeses matured for a long time are considerably safer than fresh ones.

The other routes are less common:

• raw or undercooked meat, especially liver and other offal;
• an animal's blood, birth fluids or afterbirth reaching a break in the skin or the lining of the eyes — this is how infection happens at calving and lambing;
• breathing in dust and fine droplets in barns, slaughterhouses and laboratories;
• contact with a dog brought in from a country where the disease is common.

Person-to-person spread is all but non-existent. Isolated cases through breast milk, through sex and through transfusion or transplant have been described, but the people around a patient have nothing to fear.

From infection to the first signs is usually one to four weeks, occasionally several months. With that gap, people no longer connect the illness with a trip taken earlier or with cheese bought at a market.

Who is most at risk

• people who work with livestock: farmers, vets, herders, abattoir and meat-processing staff;
• microbiology laboratory staff — this bacterium is one of the commonest causes of infection acquired at work;
• travellers who buy cheese and milk from small private producers;
• hunters who butcher a carcass without gloves;
• anyone who has brought a dog in from abroad or keeps animals at home.

How the illness shows itself

The onset can be abrupt, over a day or two, or slow, spread across several weeks. The picture resembles flu but does not resolve in a week:

• a fever that comes in waves: several hot days, then a lull, then another rise;
• drenching night sweats that mean changing the bedding;
• marked weakness and a tiredness that sleep does not repair;
• headache, loss of appetite and weight loss;
• a dull ache in the lower back, the large joints and the muscles;
• enlarged glands and a heaviness under the ribs on one side or the other.

Low mood and irritability out of all proportion to the rest of it are common too — people describe having no energy for anything at all. Untreated, the illness can run for months, quietening down and coming back.

Complications that make waiting a bad idea

The danger in brucellosis is not the fever itself but the way the bacterium settles into organs and tissues. That is why sitting it out is a poor plan.

• Spine and sacrum. The commonest complication. Persistent low back pain that builds over weeks and does not respond to the usual treatment for a bad back may mean inflammation of the vertebrae or of the sacroiliac joint.
• Heart. Inflammation of the inner lining of the heart and of the valves is uncommon, yet it accounts for most of the deaths from this disease. Increasing breathlessness, swelling and a fever that will not settle should raise the alarm.
• Nervous system. Inflammation of the linings of the brain, damage to hearing and vision, stubborn headaches and weakness in the limbs are all possible.
• Male genital tract. A painful swelling of the testicle and epididymis is sometimes what brings a man to a doctor in the first place.
• Pregnancy. In pregnancy the infection raises the risk of miscarriage and premature birth, so any suspicion of brucellosis is investigated without delay.

When to see a doctor and what to say

It is worth being seen if fever and weakness have lasted more than a week and any of the following applies:

• you drank unpasteurised milk or ate farmhouse cheese, especially while travelling;
• you ate raw or undercooked meat;
• you work with livestock or have butchered a carcass;
• you have a dog that was brought in from abroad.

Be sure to tell the doctor where you have been over recent months and what you ate. Without that sentence the diagnosis almost never comes to mind in time, and people spend weeks being investigated for a fever of unknown origin.

Do not put it off if severe back pain, breathlessness, swelling, confusion, a sudden headache with vomiting or a swollen testicle join the fever. Those signs mean the infection has moved beyond a general feeling of illness.

How the diagnosis is confirmed

The mainstays are blood culture and antibody testing; in some cases the bacterium's genetic material is looked for directly. Sometimes a sample is taken from the bone marrow, where the organism shows up more often than in blood.

One point matters a great deal. The doctor always warns the laboratory that brucellosis is suspected, because the bacterium infects staff readily through the air and has to be handled under special conditions. Beyond that, the culture is slow — anything from several days to several weeks — and a negative result reported too early rules nothing out. Antibody testing can also be negative in the first days of illness, which is why it is often repeated two or three weeks later.

Why treatment is long and uses more than one drug

Brucella lives inside human cells, where antibiotics penetrate poorly. Two features of the treatment follow from that.

First, the course is long: six weeks at the very least, and longer where the spine, the heart or the nervous system is involved, sometimes several months. Second, one drug is not enough — a combination of two or more is used, usually tetracyclines together with rifamycins or aminoglycosides. This infection is not treated with a single antibiotic, because doing so sharply raises the chance of it coming back.

People usually start to feel well again within the first weeks, and that is the most dangerous moment: an abandoned course ends in relapse. Relapse affects a minority of patients, most often within the first year, and it comes not from the bacterium becoming resistant but from its having waited out the treatment inside the cells. Where heart valves are damaged, surgery is added to the medicines.

Most people recover fully. Some report lingering tiredness and joint pain for a while after the course ends: that needs following up, but it does not always mean the infection has returned.

How to avoid catching it

There is no human vaccine against brucellosis. Everything comes down to not letting the bacterium in.

• drink only pasteurised or boiled milk; while travelling that applies to ice cream and home-made yoghurt too;
• give a miss to fresh market cheese if you do not know what milk it was made from;
• cook meat all the way through, offal above all;
• when working with animals wear gloves, eye protection and protective clothing, particularly at calving, lambing and butchering;
• cover cuts and grazes before touching livestock;
• if you are buying a dog from abroad, ask whether it has been tested.

Real protection works at the level of the farm: vaccinating stock, testing herds and removing infected animals. That is why the disease has all but vanished wherever those measures are kept up. In many countries brucellosis must be notified, and the doctor files the notification — nothing is required of the patient. Suspected cases in animals are reported to the veterinary authorities.

Online consultation

In an online appointment a doctor can go through how the fever rose and how long it lasted, ask about travel, contact with animals and what you have eaten, and judge whether the picture fits brucellosis or points elsewhere. They can explain which tests are worth doing and in what order, what the laboratory needs to be warned about, and at what point an in-person examination becomes necessary.

This material is for information only and does not replace medical advice.