|Immunohistochemical detection of C. burnetii in resected cardiac valve of a 60-year-old man with Q fever endocarditis, Cayenne, French Guiana: Monoclonal antibodies against C. burnetii and hematoxylin were used for staining; original magnification is ×50.|
|Specialty|| Infectious disease |
Q fever is a disease caused by infection with Coxiella burnetii , a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats, and other domestic mammals, including cats and dogs. The infection results from inhalation of a spore-like small-cell variant, and from contact with the milk, urine, feces, vaginal mucus, or semen of infected animals. Rarely, the disease is tick-borne. The incubation period is 9–40 days. Humans are vulnerable to Q fever, and infection can result from even a few organisms. The bacterium is an obligate intracellular pathogenic parasite.
Coxiella burnetii is an obligate intracellular bacterial pathogen, and is the causative agent of Q fever. The genus Coxiella is morphologically similar to Rickettsia, but with a variety of genetic and physiological differences. C. burnetii is a small Gram-negative, coccobacillary bacterium that is highly resistant to environmental stresses such as high temperature, osmotic pressure, and ultraviolet light. These characteristics are attributed to a small cell variant form of the organism that is part of a biphasic developmental cycle, including a more metabolically and replicatively active large cell variant form. It can survive standard disinfectants, and is resistant to many other environmental changes like those presented in the phagolysosome.
Cattle—colloquially cows—are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos taurus.
Domestic sheep are quadrupedal, ruminant mammals typically kept as livestock. Like most ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name sheep applies to many species in the genus Ovis, in everyday usage it almost always refers to Ovis aries. Numbering a little over one billion, domestic sheep are also the most numerous species of sheep. An adult female sheep is referred to as a ewe, an intact male as a ram or occasionally a tup, a castrated male as a wether, and a younger sheep as a lamb.
Incubation period is usually two to three weeks.The most common manifestation is flu-like symptoms with abrupt onset of fever, malaise, profuse perspiration, severe headache, muscle pain, joint pain, loss of appetite, upper respiratory problems, dry cough, pleuritic pain, chills, confusion, and gastrointestinal symptoms, such as nausea, vomiting, and diarrhea. About half of infected individuals exhibit no symptoms.
Fever, also known as pyrexia and febrile response, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using values between 37.5 and 38.3 °C. The increase in set point triggers increased muscle contractions and causes a feeling of cold. This results in greater heat production and efforts to conserve heat. When the set point temperature returns to normal, a person feels hot, becomes flushed, and may begin to sweat. Rarely a fever may trigger a febrile seizure. This is more common in young children. Fevers do not typically go higher than 41 to 42 °C.
Malaise is a feeling of general discomfort, uneasiness or pain, often the first sign of an infection or other disease. The word has existed in the French language since at least the 12th century.
Headache is the symptom of pain anywhere in the region of the head or neck. It occurs in migraines, tension-type headaches, and cluster headaches. Frequent headaches can affect relationships and employment. There is also an increased risk of depression in those with severe headaches.
During its course, the disease can progress to an atypical pneumonia, which can result in a life-threatening acute respiratory distress syndrome, whereby such symptoms usually occur during the first four to five days of infection.[ citation needed ]
Atypical pneumonia, also known as walking pneumonia, is the type of pneumonia not caused by one of the pathogens most commonly associated with the disease. Its clinical presentation contrasts to that of "typical" pneumonia. A variety of microorganisms can cause it. When it develops independently from another disease it is called primary atypical pneumonia (PAP).
Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath, rapid breathing, and bluish skin coloration. Among those who survive, a decreased quality of life is relatively common.
Less often, Q fever causes (granulomatous) hepatitis, which may be asymptomatic or becomes symptomatic with malaise, fever, liver enlargement, and pain in the right upper quadrant of the abdomen. Whereas transaminase values are often elevated, jaundice is uncommon. Retinal vasculitis is a rare manifestation of Q fever.
Hepatitis is inflammation of the liver tissue. Some people have no symptoms whereas others develop yellow discoloration of the skin and whites of the eyes, poor appetite, vomiting, tiredness, abdominal pain, or diarrhea. Hepatitis may be temporary (acute) or long term (chronic) depending on whether it lasts for less than or more than six months. Acute hepatitis can sometimes resolve on its own, progress to chronic hepatitis, or rarely result in acute liver failure. Over time the chronic form may progress to scarring of the liver, liver failure, or liver cancer.
Hepatomegaly is the condition of having an enlarged liver. It is a non-specific medical sign having many causes, which can broadly be broken down into infection, hepatic tumours, or metabolic disorder. Often, hepatomegaly will present as an abdominal mass. Depending on the cause, it may sometimes present along with jaundice.
The abdomen constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the frontal part of the abdominal segment of the trunk, the dorsal part of this segment being the back of the abdomen. The region occupied by the abdomen is termed the abdominal cavity. In arthropods it is the posterior tagma of the body; it follows the thorax or cephalothorax. The abdomen stretches from the thorax at the thoracic diaphragm to the pelvis at the pelvic brim. The pelvic brim stretches from the lumbosacral joint to the pubic symphysis and is the edge of the pelvic inlet. The space above this inlet and under the thoracic diaphragm is termed the abdominal cavity. The boundary of the abdominal cavity is the abdominal wall in the front and the peritoneal surface at the rear.
The chronic form of Q fever is virtually identical to inflammation of the inner lining of the heart (endocarditis), which can occur months or decades following the infection. It is usually fatal if untreated. However, with appropriate treatment, the mortality falls to around 10%.
Inflammation is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecular mediators. The function of inflammation is to eliminate the initial cause of cell injury, clear out necrotic cells and tissues damaged from the original insult and the inflammatory process, and initiate tissue repair.
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the surfaces of intracardiac devices. Endocarditis is characterized by lesions, known as vegetations, which is a mass of platelets, fibrin, microcolonies of microorganisms, and scant inflammatory cells. In the subacute form of infective endocarditis, the vegetation may also include a center of granulomatous tissue, which may fibrose or calcify.
Diagnosis is usually based on serology(looking for an antibody response) rather than looking for the organism itself. Serology allows the detection of chronic infection by the appearance of high levels of the antibody against the virulent form of the bacterium. Molecular detection of bacterial DNA is increasingly used. Culture is technically difficult and not routinely available in most microbiology laboratories.
Serology is the scientific study of serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection, against other foreign proteins, or to one's own proteins.
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen, via the Fab's variable region. Each tip of the "Y" of an antibody contains a paratope that is specific for one particular epitope on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly. Depending on the antigen, the binding may impede the biological process causing the disease or may activate macrophages to destroy the foreign substance. The ability of an antibody to communicate with the other components of the immune system is mediated via its Fc region, which contains a conserved glycosylation site involved in these interactions. The production of antibodies is the main function of the humoral immune system.
Q fever can cause endocarditis (infection of the heart valves) which may require transoesophageal echocardiography to diagnose. Q fever hepatitis manifests as an elevation of alanine transaminase and aspartate transaminase, but a definitive diagnosis is only possible on liver biopsy, which shows the characteristic fibrin ring granulomas.
Protection is offered by Q-Vax, a whole-cell, inactivated vaccine developed by an Australian vaccine manufacturing company, CSL Limited. burnetii organisms. Skin and blood tests should be done before vaccination to identify pre-existing immunity, because vaccinating people who already have an immunity can result in a severe local reaction. After a single dose of vaccine, protective immunity lasts for many years. Revaccination is not generally required. Annual screening is typically recommended.The intradermal vaccination is composed of killed C.
In 2001, Australia introduced a national Q fever vaccination program for people working in “at risk” occupations. Vaccinated or previously exposed people may have their status recorded on the Australian Q Fever Register, which may be a condition of employment in the meat processing industry. An earlier killed vaccine had been developed in the Soviet Union, but its side effects prevented its licensing abroad.
Preliminary results suggest vaccination of animals may be a method of control. Published trials proved that use of a registered phase vaccine (Coxevac) on infected farms is a tool of major interest to manage or prevent early or late abortion, repeat breeding, anoestrus, silent oestrus, metritis, and decreases in milk yield when C. burnetii is the major cause of these problems.
Treatment of acute Q fever with antibiotics is very effective[ citation needed ] and should be given in consultation with an infectious diseases specialist.[ citation needed ] Commonly used antibiotics include doxycycline, tetracycline, chloramphenicol, ciprofloxacin, ofloxacin, and hydroxychloroquine. Chronic Q fever is more difficult to treat and can require up to four years of treatment with doxycycline and quinolones or doxycycline with hydroxychloroquine.
Q fever in pregnancy is especially difficult to treat because doxycycline and ciprofloxacin are contraindicated in pregnancy. The preferred treatment is five weeks of co-trimoxazole.
The pathogenic agent is found everywhere except New Zealand.The bacterium is extremely sustainable and virulent: a single organism is able to cause an infection. The common source of infection is inhalation of contaminated dust, contact with contaminated milk, meat, or wool, and particularly birthing products. Ticks can transfer the pathogenic agent to other animals. Transfer between humans seems extremely rare and has so far been described in very few cases.
Some studies have shown more men to be affected than women,which may be attributed to different employment rates in typical professions.
“At risk” occupations include:
Q fever was first described in 1935 by Edward Holbrook Derrick in slaughterhouse workers in Brisbane, Queensland. The "Q" stands for "query" and was applied at a time when the causative agent was unknown; it was chosen over suggestions of abattoir fever and Queensland rickettsial fever, to avoid directing negative connotations at either the cattle industry or the state of Queensland.
The pathogen of Q fever was discovered in 1937, when Frank Macfarlane Burnet and Mavis Freeman isolated the bacterium from one of Derrick’s patients. It was originally identified as a species of Rickettsia . H.R. Cox and Gordon Davis elucidated the transmission when they isolated it from ticks found in the US state of Montana in 1938. It is a zoonotic disease whose most common animal reservoirs are cattle, sheep, and goats. Coxiella burnetii – named for Cox and Burnet – is no longer regarded as closely related to the Rickettsiae, but as similar to Legionella and Francisella , and is a proteobacterium.
An early mention of Q fever was important in one of the early Dr. Kildare films (1939, Calling Dr. Kildare ). Kildare's mentor Dr. Gillespie (Lionel Barrymore) tires of his protégé working fruitlessly on "exotic diagnoses" ("I think it's Q fever!") and sends him to work in a neighborhood clinic, instead.
Q fever was also highlighted in an episode of the U.S. television medical drama House ("The Dig", season seven, episode 18).
C burnetii has been developed as a biological weapon. The United States investigated it as a potential biological warfare agent in the 1950s, with eventual standardization as agent OU. At Fort Detrick and Dugway Proving Ground, human trials were conducted on Whitecoat volunteers to determine the median infective dose (18 MICLD50/person i.h.) and course of infection. The Deseret Test Center dispensed biological Agent OU with ships and aircraft, during Project 112 and Project SHAD. As a standardized biological, it was manufactured in large quantities at Pine Bluff Arsenal, with 5,098 gallons in the arsenal in bulk at the time of demilitarization in 1970. C. burnetii is currently ranked as a "category B" bioterrorism agent by the CDC. It can be contagious, and is very stable in aerosols in a wide range of temperatures. Q fever microorganisms may survive on surfaces up to 60 days. It is considered a good agent in part because its ID50 (number of bacilli needed to infect 50% of individuals) is considered to be one, making it the lowest known.
Cattle, goats, and sheep are most commonly infected, and can serve as a reservoir for the bacteria. Q fever is a well-recognized cause of abortions in ruminants and pets. C. burnetii infection in dairy cattle has been well documented and its association with reproductive problems in these animals has been reported in Canada, the US, Cyprus, France, Hungary, Japan, Switzerland, and Germany. For instance, in a study published in 2008, a significant association has been shown between the seropositivity of herds and the appearance of typical clinical signs of Q fever, such as abortion, stillbirth, weak calves, and repeat breeding. Moreover, experimental inoculation of C. burnetii in cattle induced not only respiratory disorders and cardiac failures (myocarditis), but also frequent abortions and irregular repeat breedings.
Typhoid fever, also known simply as typhoid, is a bacterial infection due to Salmonella typhi that causes symptoms. Symptoms may vary from mild to severe and usually begin six to thirty days after exposure. Often there is a gradual onset of a high fever over several days; weakness, abdominal pain, constipation, headaches, and mild vomiting also commonly occur. Some people develop a skin rash with rose colored spots. In severe cases there may be confusion. Without treatment, symptoms may last weeks or months. Diarrhea is uncommon. Other people may carry the bacterium without being affected; however, they are still able to spread the disease to others. Typhoid fever is a type of enteric fever, along with paratyphoid fever.
A vaccine is a biological preparation that provides active acquired immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as a threat, destroy it, and to further recognize and destroy any of the microorganisms associated with that agent that it may encounter in the future. Vaccines can be prophylactic, or therapeutic.
Monkeypox is an infectious disease caused by the monkeypox virus that can occur in certain animals including humans. Symptoms begin with fever, headache, muscle pains, swollen lymph nodes, and feeling tired. This is followed by a rash that forms blisters and crusts over. The time from exposure to onset of symptoms is around 10 days. The duration of symptoms is typically 2 to 5 weeks.
Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium Francisella tularensis. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infection may occur.
Babesiosis is a malaria-like parasitic disease caused by infection with Babesia, a type of Apicomplexa. Human babesiosis transmission via tick bite is most common in the Northeastern and Midwestern United States and parts of Europe, and sporadic throughout the rest of the world. It occurs in warm weather. People can get infected with Babesia parasites by the bite of an infected tick, by getting a blood transfusion from an infected donor of blood products, or by congenital transmission. Ticks transmit the human strain of babesiosis, so it often presents with other tick-borne illnesses such as Lyme disease. After trypanosomes, Babesia is thought to be the second-most common blood parasite of mammals, and they can have a major impact on health of domestic animals in areas without severe winters. In cattle the disease is known as Texas cattle fever, redwater, or piroplasmosis.
Brucellosis is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meat from infected animals, or close contact with their secretions. It is also known as undulant fever, Malta fever, and Mediterranean fever.
Scrub typhus or bush typhus is a form of typhus caused by the intracellular parasite Orientia tsutsugamushi, a Gram-negative α-proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan.
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.
Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. Tick-borne illnesses are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. Because individual ticks can harbor more than one disease-causing agent, patients can be infected with more than one pathogen at the same time, compounding the difficulty in diagnosis and treatment. As of 2016, 16 tick-borne diseases of humans are known.
Bartonellosis is an infectious disease produced by bacteria of the genus Bartonella. Bartonella species cause diseases such as Carrión´s disease, trench fever, cat-scratch disease, bacillary angiomatosis, peliosis hepatis, chronic bacteremia, endocarditis, chronic lymphadenopathy, and neurological disorders.
Meningococcal disease describes infections caused by the bacterium Neisseria meningitidis. It has a high mortality rate if untreated but is vaccine-preventable While best known as a cause of meningitis, it can also result in sepsis, which is an even more damaging and dangerous condition. Meningitis and meningococcemia are major causes of illness, death, and disability in both developed and under-developed countries.
Babesia, also called Nuttallia, is an Apicomplexan parasite that infects red blood cells, transmitted by ticks. Originally discovered by the Romanian bacteriologist Victor Babeș, over 100 species of Babesia have since been identified.
Anaplasma phagocytophilum is a Gram-negative bacterium that is unusual in its tropism to neutrophils. It causes anaplasmosis in sheep and cattle, also known as tick-borne fever and pasture fever, and also causes the zoonotic disease human granulocytic anaplasmosis.
A rickettsiosis is a disease caused by intracellular bacteria.
Southern tick-associated rash illness (STARI) or Masters' disease is an emerging infectious disease related to Lyme disease that occurs in southeastern and south-central United States. It is spread by tick bites, but the organism that causes the infection is unknown.
Human granulocytic anaplasmosis (HGA) is a tick-borne, infectious disease caused by Anaplasma phagocytophilum, an obligate intracellular bacterium that is typically transmitted to humans by ticks of the Ixodes ricinus species complex, including Ixodes scapularis and Ixodes pacificus in North America. These ticks also transmit Lyme disease and other tick-borne diseases.
A pneumococcal infection is an infection caused by the bacterium Streptococcus pneumoniae, which is also called the pneumococcus. S. pneumoniae is a common member of the bacterial flora colonizing the nose and throat of 5–10% of healthy adults and 20–40% of healthy children. However, it is also a cause of significant disease, being a leading cause of pneumonia, bacterial meningitis, and sepsis. The World Health Organization estimate that in 2005 pneumococcal infections were responsible for the death of 1.6 million children worldwide.
African tick bite fever (ATBF) is a bacterial infection spread by the bite of a tick. Symptoms may include fever, headache, muscles pains, and a rash. At the site of the bite there is typically a red skin sore with a dark center. Onset usually occur 4–10 days after the bite. Complications are rare, however may include joint inflammation. Some people do not develop symptoms.