Q Fever (Coxiellosis)

Q Fever (Coxiellosis) is a zoonotic disease. The letter “Q” represent an abbreviated form of a query because of unknown descriptions for the disease that occured before proper diagnosis had been done.

Q Fever is a notifiable, occupational hazard of animal handlers and farm workers. Sudden onset of acute fever and liver infection followed by chronic endocarditis is observed.

Q Fever (Coxiellosis) is a chronic debilitating and fatal disease in animals and humans.

Etiology

• It is caused by Coxiella burnetii.
• It is an obligate, intracellular parasite, gram negative, non-motile pleomorphic – ovoid to rod shaped organism.
• It exists in two antigenic phases: Phase-I – more infectious.
• The organism is resistant to external environmental influences.
• It has been divided into 6 genomic groups on the basis of restriction fragment length polymorphism.

Epidemiology

Prevalence of infection

• The disease is worldwide in distribution.
• The organism prevails in a wide range of wildlife species and their ecto-parasites.
• The rates of infection varies between farm animals, locations, regions and countries.
• In cattle, the prevalence of 6-82% and 23-96% of herds has been reported.
• The prevalence is significantly higher in cattle as compared to sheep and goats.
• Ticks and feral animals maintains the organism.
• Worldwide except in New Zealand the disease has been distributed.

Predisposing factors

• Those who with pre existing valvular heart disease and vascular graft done.
• Transplant recipients.
• Patients with cancer.
• Those with chronic kidney disease are at risk of developing chronic Q fever.

Source of infection

• Infection spread by contact and inhalation.
• In pregnant animals recrudescence of infection occurs and the organism excreted from intestine, uterus, placenta, udder during parturition.
• Placenta, fetal fluids, vaginal fluids, and urine consist of highly significant concentration of the organism.
• The organism excreted through the feces of sheep from 11-18 days post-partum.

Transmission

• Parturient period may be the major period for transmission of infection.
• The organism present in the semen of sero-positive bulls and venereal transmission is suspected.
• More than 40 species of ticks infected and transmit the infection by transovarian mode.
• Feces contains 10¹⁰ infectious units/1g of of feces.
• The organism survive for 1 year at an ambient temperature

Transmission in Human

• Human acquires the infection by inhalation of infected airborne dust, contact with infected soil, wool, urine, feces, reproductive discharges, and other inanimate objects.
• Using the infected ovine manures as a garden fertilizers spread the infection in human.
• Sheep is a major reservoir of infection for humans.
• Urban population as they have close association with large dairy herds increasingly susceptible to infection due to their reservoir status.
• Drinking of infected milk from cattle, sheep and goats transmits the infection, however, pasteurization kills the organism. It is also an occupational hazard in human (veterinarians, livestock dealers, dairy plant, slaughter house workers, shearers), who are having close contact with infected domestic animals and their products.
• Several incidences in sheep attributed to parturient period in sheep and goats.
• In human, tick bite and human to human contact also transmits infection.

Host Affected

• Sheep are at greater risk for infection.
• Cattle, sheep and goats are main reservoir of infection for humans.
• Non-pregnant animals maintained the silent infection followed by latency until the animals get pregnant.

Pathogenesis

• Coxiella multiply in trophoblast of placenta.
• Unpasteurised milk has 10⁵ organisms/ml of milk.
• Infective dose for human is approximately one organism as it is highly infectious.
• Infection ensues abortion, stillbirth, and poorly viable lambs.
• Lambs born to ewes excreting the organism are found to be clinically normal.

• Though there is no abortion occurs in successive pregnancy in sheep but resurgence of infection occurs with excretion of organism immediately after the parturition.
• Goats excrete the organism in milk and feces for upto 2 weeks to 52 days following kidding.
• In cattle maximum shedding occurs for 2 weeks but in milk, cattle sheds for 2 years.
• Goats also affected with abortion.

Clinical Signs

In Animals

• Infection in ruminants occurs at any time usually clinically in-apparent.
• Abortion in sheep and goats during later part of the lambing period in the flock and in the latter period of pregnancy in an individual ewes.
• Correlation between herd level seroprevalence and herd infertility are clear.
• In pregnant animals, abortion, still birth, metritis, retained placenta, infertility and a prematurity occurs due to transplacental transmission, sometimes between 306 weeks of pregrancy.
• The interval between primary infection and the first signs of endocarditis last between 6 months and 10 years.

In Humans

Acute Infection

• Mostly half of the infected human population shows clinical signs. Immuno-compromised persons are at greater risk for disease.
• Sudden onset of high fever (104-105oF), sweat, non productive cough, severe headache, general malaise, myalgia, confusion, sore throat, chills, nausea, vomition, diarrheoa, abdominal pain, chest pain etc.,
• Fever last for 1-2 weeks, weight loss persists for some time. About 30-50% of patients suffering from pneumonia.
• Liver function tests indicates the presence of hepatitis. Most of the acutely infected persons recover from infection and only 1-2% die of acute Q.fever.
• Prevalence of infection in farm animals leads to subsequent increased infection in humans.
• It is considered as a potential agent of bio-terrorism.

Chronic Infection

• Persists for more than 6 months and is a much more severe disease and is uncommon.
• Within a year, the infection in acutely infected people become chronic and persists as long as 20 years.
• A serious complication of Q.fever is endocarditis, generally having aortic heart valves and less in mitral valves.
• Less commonly pneumonitis, hepatitis, meningoencephalitis.
• Endocarditis, and hepatitis are highly manifested during chronic infection.
• About 65% of the people with chronic Q.fever may die of disease.
• It has shorter incubation period for 2-3 weeks.
• If people recover from infection will develop life long immunity against re-infection.

Necropsy Findings

The liver, lungs, kidneys of the aborted fetuses shows occassionally foci of necrosis and inflammation.

Placenta shows thickening and purulent exudate and large red brown foci of necrosis in its inter-cotyledonary areas.

Diagnosis

• Based on clinical signs and necropsy findings.
• Identification of organism.
• Isolation of organism: Even the repeated blood culture shows negative results.
• Decreased platelet count and thrombocytopenia.
• Q.fever hepatitis is characterized by small granulomas with epitheloid cells in rosette formation.
• Serological detection of phase variants of antibody by Complement fixation test, micro-aggluatination test, ELISA, indirect fluorescence and indirect immuno-fluorescence test can be carried out.
• Phase-II antibody is associated with recent and acute infections and phase I with chronic infection.
• Abnormal liver function test shows the increase in bilirubin and alkaline phosphatase.

Sample Collection

From buffy coat of blood and necrotic tissue material.

Differential Diagnosis

• Ornithosis
• Mycoplasmal pneumonia
• Atypical pneumonias
• Salmonellosis
• Leptospirosis

Treatment

• Doxycycline within the first 3 days of illness 100 mg/oral twice daily for 15-21 days.
• Hydroxyquinolone 200mg thrice a day for 3-6 months.
• Tetracycline 500 mg 4 times a day i/v or oral 2-3 weeks.
• Combination of Pefloxacin 800mg/day and Rifampicin 1,200 mg/day.
• Choramphenical 500mg 4 times a day.

Prevention

• Vaccine: Australia-Q.Vax : Inactivated phase I antigen, 0.5 ml S/C upper arm.
• Immunity lasting for 5 years.
• Embryonated inactivated hens eggs vaccine has been used in US.
• Vaccine trial with killed vaccine, show good persistent antibody response and suggest that vaccination can limit the excretion of the organism.

Control

• The organism is sensitive to sodium hypochlorite, 1:100 lysol solution and formalin fumigation provided a high humidity is maintained.
• Animals should be isolated for 3 weeks after abortion and aborted fetus and placental contaminant should be burnt and decomposed for 6month prior to be used as fertilizers to the fields.
• There is no national and international control strategies based on control in animal population.
• Pasteurisation of milk.