It is a zoonotic disease caused by Coxiella burnetii and mostly occurs in farm animals. The disease has drawn much attention in the recent past for its use as an agent of bioterrorism.
Distribution
It has go global distribution. But, the disease is absent in New Zealand and Antarctica. The disease of late has been reported from Canada, France, Australia, Germany, Japan, Spain, Switzerland, UK and USA.
In a survey in Punjab by capillary agglutination test on 1342 man, 130 cattle, 52 buffaloes, 441 goats, 219 sheep, 52 swine and 21 dog, it was observed that 25.5%, 16.2%, 9.6%, 6.1%, 3.7%, 0% were seropositive respectively indicated its presence in Delhi and Karnataka.
The organism has been isolated from Uttar Pradesh. It may appear as emerging zoonoses in any part of the country.
Aetiology
The disease was first detected in Queensland, Australia in 1935. The disease was termed as Query (Q) fever since the itiopathogenesis was not determined at that time. Subsequently after some time it was reported that the agent for this disease is an obligate intra cellular rickettsia. It was named as Coxiella burnetii. The name thus given is due to two scientists honour. They are Harod cox and Mac fariance Burnetii. The organism coxiella is considered as rickettsia. This belongs to the order Legionellate, Family coxiellacleae. It is a gram negative coccobacillary organism which used to reside and replicate in the host macrophage and monocytes.
The organism is fairly resistant to physical and chemical agents. It can remain viable in the soil and congenital environment for many months. It is amenable to sodium hypochlorite, 1:100 lysol solution and fumigation with high humidity.
There is strain variation of it. The differences is only plasmid based. The organism is highly pathogenic. Only one organism even may be enough to induce infection to man.
Susceptible Hosts
Domestic animals may suffer. Cattle, sheep, goat are the important victims. Dog and cat may suffer. It is recorded from monitor, tortoise, python, water and rat snakes. Man is also susceptible. Thus, it is a zoonotic disease. Wild animals, like sare hares, mouse, white tailed deer, black near, Kangaroo, ferret, goats, wild rabbits may suffer. Some time wild birds prove to be sero-positive.
Mode of Transmission
Transmission usually takes place in four ways i.e., (a) Inhalation (b) Ingestion (c) Contact (d) Vector
(a) Inhalation
- Soil contaminated dust
- Air borne dust
- Contaminated wool dust
- Contaminated bedding
- The above materials are contaminated by infected urine or faeces
(b) Ingestion
- Ingestion of contaminated milk
- Ingestion of contaminated genital discharges
- Ingestion of contaminated foetus or placenta
- Ingestion of contaminated bedding materials or manure
- Man may contract the exposure through parturient small ruminants
(c) Contact
- Persons who come in contact through their occupations e.g. farm workers, veterinarians, live stock dealers, dairy plant worker, shearers, slaughter house workers. Venereal transmission suggested through semen. Wild rodents may play some role in transmission to domestic animals and man.
(d) Vector
- C. burnetii may infect around 40 species of ticks.
- Ticks are the reservoirs and vector of transmission.
Pathogenesis
The agent has got to distinct cycle:
(a) Large Cell Variant (LCV): This is he vegetative form remain within the cells.
(b) Small Cell Variant (SCV): This is extracellular and inactive in nature.
Sequence that follows is as under there may lysis or binary fission of unequal cell division of LCV.
- There is entry of the spore or SCV in the eukaryotic cell and acidification of endosomes of phagosomes.
- There is multiplication of small cell variants (SCV) by binary fission and differentiation to large cell variants (LCV).
- There is fusion of the endosome with lysosome and acidification of the phagolysosome.
- There is multiplication of LCV by transverse binary fission, differentiation of LCV to SCV and development of the polar endospore in LCV.
- There is release of the spore and SCV out of the cell.
The SCV and SDC (small dense cells) are considered as the resistant form of C. burnetii which is highly resistant to UV radiation, heat, dessication and sonication as well as osmotic and oxidative stress. This power of resistance makes the organisms to survive as infectious agent for atleast 150 days. This is the reason the organism contaminate the environment for a long time and thus infect man and animals.
Coxiella expressing a complete LPS structure are characterized as virulent phase 1 bacteria. LPS of the organism has an endotoxic activity which induces the production of inflammatory cytokines in marine and human macrophages. Avirulent phase 2 are produced by spontaneous mutations of large genetic rearrangements. This phase variations is observed when Coxiella organisms are propagated in non-immuno competent cell cultures. The transition between the two phases is perhaps a strategy of Coxiella to by pass the immune response of the host but phase 2 bacteria have not yet been isolated from host.
Clinical Findings
The clinical signs in Q-fever is usually in apparent in live stock. Anorexia, high rise of temperature is the initial signs.
But most striking manifestation is abortion. Besides, there may be still birth, dystocia and occasionally pneumonia.
Abortion occurs at the latter part of pregnancy. There may not be any apparent signs prior to abortion. Aborted foetus appear grossly normal but with thin condition. The abortion rate ranges from 3 to 8%. In cattle, metritis is the cardinal manifestation. Aborted females used to recover quickly but does not abort in the next gestation usually. Metritis may persist. Organisms may be shared through milk, urine and faeces. ‘Abortion storm’ appears in herd.
Lesions
There is not much gross changes, placenta of aborted animals is thickened and there is purulent exudates. There is inter cotyledonary fibrous thickening. A severe inflammatory changes is observed in the myometrium and stroma adjacent to the placental area during gestation in goats. Necrotizing placentitis is observed with trophoblast cells having well defined inclusion also found in multinuclear cells.
Diagnosis
The diagnosis is based on:
- Isolation and identification of the agent: This can be had by experimental transmission, tissue culture or developing egg embryo. This is required to be made in laboratory having Bio-safety level-3.
- Serological test: It includes IFA, ELISA and CFT.
- Antigen detection assay: Immuno histo-chemical staining (IHC).
- Nucleic acid detection PCR: The PCR is the most sensitive and rapid detection tool.
Treatment
In animals, tetracycline @ 8 mg/kg PO may be administered in water for several weeks. In man, Doxycycline for 18-36 day be used. Valvar defects may require surgical interference.
Q-Fever in Man
Many of the cases remain asymptomatic. But, most shows flu like symptoms. This is manifested as high rise of temperature, severe headache, weight loss, myalgia and cough. Skin rashes may appear in some subjects.
Symptoms of hepatitis may be the feature. Hepatitis may lead to jaundice and is having a long course of fever. Granulomatous hepatitis may occur. The hepatitis may bring about symptoms like headache, myocarditis, pericarditis, pancreatitis, meningoencephalitis and abortion.
There may be fatal endocarditis in 1-2% cases. Endocarditis is one of the most significant manifestation in man. Persons having underlying heart valve abnormalities, prosthetic valves or immune comprised are at increased risk of Q fever.
In man, another manifestation is recorded known as ‘Chronic fatigue syndrome’. This is out lined as fatigue, myalgia, night sweating and changes in mood and sleep patterns. Pregnant lady may suffer from placentitis leading to abortion.
Control
- Man to man transmission does not occur.
- Air-borne transmission is possible thus infected one should be segregated from the healthy animal and man.
- New animal without serological test should not be given entry to the herd.
- Vectors are to be eliminated as far as possible with appropriate acaricides.
- The premises and the utensils should be disinfected thoroughly.
- Placenta to be disposed of readily in order to avoid ingestion by the contact animal.
- Manure should be covered with lime.
- People who come in contact like farm people, veterinarians should keep themselves away from milk and uterine discharges. They should handle only when the animal is sero-negative.
Vaccines
- Inactivated killed vaccine is used in animals with fair success.
- Formalin killed whole cell vaccine is used in man. Commercial vaccine (Q-vax, CSL limited, Parkville Victoria, Australia) is available for man.
Bioterrorism
C. burnetii is used as potential agent for bioterrorism. It is suited for the above purpose.
Reason being:
- Low infectious dose
- Resistance to numbers of agents
- Wide host range
- Aerosol spread
- Least environmental degradation
