Coxiella burnetii is a rod-shaped bacterium that can cause Q fever in humans. The protozoan lives as a parasite within cells and is commonly transmitted from animals to humans. In addition, it finds use as a biological weapon.
What is Coxiella burnetii?
Coxiella burnetii is a rod-shaped bacterium. The single-celled organism lives aerobically: it requires oxygen to carry out metabolic processes. At 0.4 µm, Coxiella burnetii is a relatively small bacterium. Biology does not classify it as a coccoid bacteria, which are spherical, but often describes it as “almost coccoid.” Coxiella burnetii causes Q fever (query fever) in humans. The pathogen belongs to the Coxiellaceae family. Originally, biologists assumed Coxiella burnetii belonged to the Rickettsiaceae family. This group of bacteria includes many pathogens that, like Coxiella, live as parasites in a host and feed on it. However, modern genetics has demonstrated that the genome of Coxiella burnetii is very different from that of the Rickettsiaceae. This rules out its membership in this family. In the course of these investigations, researchers also found that Coxiella does not belong to the same class as the Rickettsiaceae. The bacterium thus provides an illustrative example of the importance of modern genetic studies for the systematics of living organisms. In the case of pathogens, the correct classification has great practical significance: the better a bacterium is studied, the more effective treatments are possible.
Occurrence, distribution, and characteristics
As a parasite, Coxiella burnetii requires a host to survive permanently. However, the bacterium can survive for a time without a host. Under these living conditions, its cell wall thickens, forming a protective shield against the outside world. It is also responsible for the fact that the unicellular organism is more resistant than other bacteria. Drought can hardly harm it; even after several months without liquid, Coxiella remains active and infectious. However, the thickened cell wall also brings disadvantages for Coxiella burnetii: the extra cell mass must be constantly repaired and renewed to maintain protection. Maintenance consumes not only energy but also building materials. In addition, a thicker cell wall makes it more difficult to transport nutrients into the cell. Also, waste products that the bacterium excretes can only be disposed of with increased effort. Therefore, the cell wall thins as soon as Coxiella burnetii is inside a host cell. Such a host can be, for example, a cell in the body of a human. The bacterium penetrates the membrane of the human cell and surrounds itself with a vacuole. A vacuole is a cavity within the cell that can move like a bubble within the host cell. A membrane demarcates the vacuole from the outside. Inside the host cell, Coxiella burnetii affects the cell’s metabolism, altering it so that the cell no longer functions properly. As a result, it triggers a variety of symptoms. Sheep are the main carriers of Coxiella burnetii. Somewhat less frequently, the bacterium reaches humans via goats or cattle. Dogs, cats and other domestic animals are also possible carriers. Ticks mostly help Coxiella burnetii spread among animal hosts; in principle, it is possible for humans to become infected this way as well. Coxiella burnetii is highly infectious. Medicine considers the bacterium to be one of the most infectious microorganisms of all. Scientists measure how infectious a pathogen is using the ID50. This is the dose needed to infect 50% of the test animals with the disease. For Coxiella burnetii, the ID50 is 1. Only 1-10 bacteria are needed to cause infection. Even one bacterium entering the body can spread rapidly through cell division and infect a critical number of cells.
Symptoms, complaints, and signs
The coxielle burnetii pathogen can lead to goat flu or Q fever. This illness is manifested by a number of distinct symptoms. Initially, general signs of illness such as fever, weakness, and headache present themselves.The body temperature continues to rise in the course of the disease and eventually leads to serious circulatory problems. Many sufferers also complain of muscle or limb pain, particularly in the hands and thighs, depending on where the pathogens are located. Furthermore, the disease can cause chills and a strong feeling of malaise. These complaints are accompanied by a general weakness. The mental and physical performance decreases massively and the affected person usually can no longer participate in working life. The severe form of Q fever causes serious symptoms after only a few days. If the disease is not treated quickly, the pathogen can cause pneumonia or even hepatitis. In less severe cases, the symptoms of the flu subside after about a week to ten days. Externally, an infection with Coxiella burnetii is not recognizable. However, the symptoms evoke the typical signs of illness, i.e., pale skin, sweating, and darkly discolored eye rims.
Complications
In most cases, Coxiella burnetii causes the so-called Q fever. This fever can be very dangerous for humans and in the worst case can also lead to death. As a rule, the lungs become inflamed. The liver can also be damaged by inflammation. The affected person suffers from the usual symptoms of fever and flu. He feels weak and exhibits pain in the extremities and muscles. Likewise, there is a chill and a general feeling of illness. The affected person has no appetite and loses weight as a result. Due to the discomfort in the lungs, there is usually a cough, which may be associated with blood. The immune system is extremely weakened by the disease and can even lead to pericarditis. It is not uncommon for women who have the disease to suffer a miscarriage. Although the fever is relatively contagious, it can be treated well so that no further complications occur after treatment. Treatment is causal and symptomatic, but must begin early. Without treatment, the disease is usually fatal to the patient.
When should you see a doctor?
When high fever, muscle pain, and other characteristic symptoms of Coxiella burnetii are noted, a physician should be consulted. If caught early, the chances of recovery from Q fever are relatively good. At the latest, when signs of liver, heart or brain inflammation appear, it is recommended to go to the nearest hospital. The same applies to coughing up blood or cardiovascular complaints. Affected women should talk to their gynecologist. Pregnant women are at increased risk of miscarriage – so be sure to see a doctor and have the fever clarified. Also, complaints that increase rapidly and do not subside after the usual time are best presented to a doctor. Medical clarification and treatment is necessary simply because of the risk of infection. If left untreated, Coxiella burnetii is usually fatal. Therefore, should severe complications develop, it is imperative that this be examined by a physician and treated if necessary. In addition to the family doctor, a cardiologist or a specialist in internal medicine can also be consulted, depending on the symptoms. If the symptoms worsen rapidly, the emergency medical service should be contacted.
Outlook and prognosis
Coxiella burnetii has an individual prognosis. With the onset of Q fever, recovery may occur within a few weeks. Symptoms are flu-like and are treated with medication. As soon as the patient takes sufficient rest and follows the doctor’s instructions, freedom from symptoms can be achieved after 2-3 weeks. In these cases, secondary symptoms are not to be expected. However, without medical care, death of the affected person is also a possible course in the worst case. In the worst case, Coxiella burnetii can cause damage to the organs. Inflammation of the lungs or liver is possible. Depending on the severity of the inflammation, the age of the patient as well as existing pre-existing diseases, an unfavorable course of the disease may result. In the case of a weakened immune system, the healing process is severely delayed or the body fails to heal the inflammation. In addition to respiratory disorders as well as the development of an anxiety disorder, functional failures of the organs are possible.These pose a potential threat to the patient’s life. If the diagnosis is made early and treatment is started quickly, a favorable prognosis can be expected. However, if the affected person also suffers from mental impairment, recovery is difficult. Recurrence of Coxiella burnetii is possible at any time with the same prognosis.
Diseases and symptoms
Coxiella burnetii causes what is known as Q fever (query fever) in humans and animals. Australian pathologist Edward Holbrook Derrick first described the reportable disease in 1937, calling the fever “query” because the bacterial cause was unknown at the time. Derrick came across Q fever when several workers in a slaughterhouse fell ill with the previously unknown fever. In all likelihood, they had contracted the disease from infected animal carcasses. Globally, Coxiella burnetii is found almost all over the world. The only exceptions are New Zealand and Antarctica. However, Q fever tends to manifest itself in different ways. Doctors in North America often first diagnose pneumonia. In contrast, in Europe, the disease is often noticed by liver inflammation. In humans, Coxiella burnetii usually causes only mild symptoms. About half of those infected suffer from flu-like signs such as fever, muscle aches, headache, feeling weak, chills, cough, and loss of appetite. Gastrointestinal symptoms are less common but may also occur. Infection often leads to inflammation of the lungs and/or liver. Inflammation is an immune system response to fight the invader. While Q fever is highly contagious, it is usually not fatal. However, long-term consequences are possible, which in extreme cases can lead to miscarriages and malformations, among other things. In chronic Q fever, Coxiella burnetii triggers pericarditis. Without treatment, chronic Q fever is often fatal.
Follow-up
With Coxiella burnetii, there are usually few measures or options available to the affected person for aftercare. With this disease, comprehensive treatment of the disease must be done to prevent further complications or further worsening of symptoms. The earlier the disease Coxiella burnetii is detected, the better is usually the further course. The disease itself can be treated relatively well with the help of medication. There are no particular complications. The patient should rest and take care of his body, and strict bed rest should be observed. When taking the medication, it should also be noted that a doctor should always be consulted first if there are any questions or if anything is unclear. Since Coxiella burnetii can also have a negative effect on the patient’s breathing, smoking should be completely avoided. Loving care and support from one’s family or friends also have a positive effect on the course of this disease. As a rule, Coxiella burnetii does not reduce the life expectancy of the affected person if the disease is detected early.
What you can do yourself
To avoid further complications or disorders, the patient should temporarily stay away from animals. Until it is clear by what route the pathogens were able to enter the organism, protective measures are advisable. In particular, it must be prevented that further bacteria or germs can infest the patient. Since the disease can be fatal without medical care, a visit to the doctor is advisable. The instructions of the physician must be followed to prevent a life-threatening condition from developing. The patient must refrain from taking medication on his or her own responsibility. This applies in particular to painkillers. Due to the numerous risks and side effects, the risk of complications is significantly increased. Various measures should be taken to stabilize mental strength. A fundamentally positive attitude to life is helpful in coping with the symptoms. In addition, the organism can be supported by a balanced and healthy diet. This enables the body’s immune system to mobilize sufficient defenses to reduce pathogens. Sick people should pay attention to good sleep hygiene. Sufficient and above all restful sleep is important.The air should be supplied with sufficient oxygen. Harmful substances such as alcohol, nicotine or drugs should always be avoided. They deprive the organism of important forces in coping with the disease.
