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Zoonoses



Excerpts have been reprinted with permission from the APHA’s Control of Communicable Diseases Manual (CCDM). Please refer to the CCDM for complete information about each disease.


BRUCELLOSIS    ICD-9 023; ICD-10 A23
(Undulant fever, Malta fever, Mediterranean fever)

1. Identification – A systemic bacterial disease of acute or insidious onset, with continued, intermittent or irregular fever of variable duration; headache; weakness; profuse sweating; chills; arthralgia; depression; weight loss and generalized aching. Localized suppurative infections of organs, including liver and spleen, as well as chronic localized infections may occur; subclinical disease has been reported. The disease may last days, months or occasionally a year or more if not adequately treated.

Osteoarticular complications occur in 20%-60% of cases; sacroiliitis is the most frequent joint manifestation. Genitourinary involvement is seen in 2%-20% of cases, with orchitis and epididymitis as common manifestations. Recovery is usual but disability is often pronounced. The case-fatality rate of untreated brucellosis is 2% or less and usually results from endocarditis caused by Brucella melitensis infections. Part or all of the original syndrome may reappear as relapses …

Laboratory diagnosis is through appropriate isolation of the infectious agent from blood, bone marrow or other tissues, or from discharges. Current serological tests allow a precise diagnosis in over 95% of cases, but it is necessary to combine a test (Rose Bengal and seroaglutination) detecting agglutinating antibodies (IgM, IgG and IgA) with others detecting non-agglutinating antibodies (Coombs-IgG or ELISA-IgG) developing in later stages. These methods do not apply for B. canis, where diagnosis requires tests detecting antibodies to rough-lipopolysaccharide antigens.

2. Infectious agents – Brucella abortus, biovars 1-6 and 9; B. melitensis, biovars 1-3; B. suis, biovars 1-5; B. canis.

3. Occurrence – Worldwide, especially in Mediterranean countries (Europe and Africa), Middle East, Africa, central Asia, central and South America, India, Mexico … Brucellosis is predominantly an occupational disease of those working with infected animals or their tissues … Sporadic cases and outbreaks occur among consumers of raw milk and milk products (especially unpasteurized soft cheese) from cows, sheep and goats. Isolated cases of infection with B. canis occur in animal handlers from contact with dogs …

4. Reservoir – Cattle, swine, goats and sheep. Infection may occur in bison, elk, caribou and some species of deer. B. canis is an occasional problem in laboratory dog colonies and kennels; a small percentage of pet dogs and a higher proportion of stray dogs have positive B. canis antibody titres. Coyotes have been found to be infected.

5. Mode of transmission – Contact through breaks in the skin with animal tissues, blood, urine, vaginal discharges, aborted fetuses and especially placentas; ingestion of raw milk and dairy products (unpasteurized cheese) from infected animals. Airborne infection occurs in pens and stables for animals, and for humans in laboratories and abattoirs …

6. Incubation period – Variable and difficult to ascertain; usually 5-60 days; 1-2 months commonplace; occasionally several months.

7. Period of communicability – No evidence of person-to-person communicability.

8. Susceptibility – Severity and duration of clinical illness vary …

9. Methods of control – The control of human brucellosis rests on the elimination of the disease among domestic animals.

A. Preventive measures:
1)   Educate the public (especially tourists) regarding the risks associated with drinking untreated milk or eating products made from unpasteurized or otherwise untreated milk.
2)   Educate farmers and workers in slaughterhouses, meat processing plants and butcher shops as to the nature of the disease and the risk in handling carcases and products from potentially infected animals, together with proper operation of abattoirs to reduce exposure (especially appropriate ventilation).
3)   Educate hunters to use protective outfits (gloves, clothing) in handling feral swine and to bury the remains.
4)   Search for infection among livestock by serological testing and by ELISA or testing of cows' milk ("ring test"); eliminate infected animals (segregation and/or slaughtering) …
5)   Rev 1 is resistant to streptomycin, and RB51 to rifampicin. This must be taken into account when treating human cases of animal vaccine infections …
6)   Pasteurize milk and dairy products from cows, sheep and goats. Boiling milk is effective when pasteurization is impossible.
7)   Exercise care in handling and disposal of placenta, discharges and fetuses …

B. Control of patient, contacts and the immediate environment:
1)   Report to local health authority: Case report obligatory in most countries …
2)   Isolation: Draining and secretion precautions if there are draining lesions; otherwise none.
3)   Concurrent disinfection: Of purulent discharges.
4)   Quarantine: Not applicable.
5)   Immmunization of contacts: Not applicable.
6)   Investigation of contacts and source of infection: Trace infection to the common or individual source …
7)   Specific treatment: A combination of rifampicin (600-900 mg daily) or streptomycin (1 gram daily), and doxycycline (200 mg daily) for at least 6 weeks is the treatment of choice. In severely ill toxic patients, corticosteroids may be helpful. Tetracycline should preferably be avoided in children under 7 to avoid tooth staining. Trimethoprim-sufamethoxazole is effective, but relapses are common (30%). Relapses occur in about 5% of patients treated with doxycycline and rifampicin and are due to sequestered rather than resistant organisms; patients should be treated again with the original regimen …

C. Epidemic measures: Search for common vehicle of infection, usually raw milk or milk products, especially cheese, from an infected herd. Recall incriminated products; stop production and distribution unless pasteurization is instituted.

D. Disaster implications: None.

E. International measures: Control of domestic animals and animal products in international trade and transport …

F. Measures in the case of deliberate use: Their potential to infect humans and animals through aerosol exposition is such that Brucella species may be used as potent biological weapons.

HENDRA AND NIPAH VIRAL DISEASESICD-9 078.8; ICD-10 1333.8
 
1. Identification – These are newly recognized zoonotic viral diseases named for the locations in Australia and Malaysia where the first human isolates were confirmed in 1994 and 1999, respectively. Nipah virus manifests mainly as encephalitis; Hendra virus as a respiratory illness (2 cases) and as a prolonged and initially mild meningoencephalitis (1 case). The full course and spectrum of these diseases is still unknown; symptoms range in severity from mild to coma and death and include fever and headaches, sore throat, dizziness, drowsiness and disorientation. Pneumonitis was prominent in the initial Hendra cases, one of which was fatal. Coma usually leads to death in 3-30 days. The case-fatality rate for clinical cases is about 50%; subclinical infections occur.
Serological diagnosis is available through detection of IgM and IgG with an antibody capture ELISA or serum neutralization. Virus isolation from infected tissues confirms the diagnosis.
 
2. Infectious agent – Hendra (formerly called equine morbillivirus) and Nipah viruses are members of a new genus, Henipaviruses, of the Paramyxoviridae family.
 
3. Occurrence – Hendra virus caused disease in horses in Queensland, Australia. In 1994, 3 human cases followed close contact with sick horses, the first 2 during the initial outbreak in Hendra, the 3rd occurring 13 months after an initially mild meningitic illness when the virus reactivated to cause a fatal encephalitis. Nipah virus affected swine in the pig-farming provinces of Perak, Negeri Sembilan, and Selangor in Malaysia. The first human case is believed to have occurred in 1996; although the disease became apparent in late 1998, most cases were identified in the first months of 1999, with over 100 confirmed deaths as of mid-1999. During 1999 11 abattoir workers in Singapore developed Nipah virus infection following contact with pigs imported from Malaysia.
 
4. Reservoir – Fruit bats for Hendra virus; virus isolation and serological data suggest that Nipah virus may have a similar reservoir. Hendra virus (in horses) and Nipah virus (domestic swine) cause an acute febrile illness, which may lead to severe respiratory and CNS involvement and death. Dogs infected with Nipah virus show a distemper-like manifestation but their epidemiological role has not been defined. Nipah-seropositive horses have been identified, but their role is also undetermined. Testing of other animals is under way; susceptibility testing suggests that cats and guineapigs can be infected, sometimes with fatal outcomes, mice, rabbits and rats appear refractory to infection.
 
5. Mode of transmission – Primarily through direct contact with infected horses (Hendra) or swine (Nipah) or contaminated tissues. Oral and nasal routes are suspected in most cases. There is no evidence for person-to-person transmission.
 
6. Incubation period – From 4 to 18 days, occasionally up to several months.
 
7. Period of communicability – unknown.
 
8. Susceptibility – undetermined-recurrent infection appear to occur.
 
9. Methods of control
A. Preventive measures: Health education about measures to be taken and the need to avoid fruit bats.
 
B. Control of patient, contacts, and the immediate environment:
1)   Report to local authority: Case report should be obligatory wherever these diseases occur…
2)   Isolation: Of infected horses or swine; no evidence for person-to-person transmission.
3)   Concurrent disinfection: Slaughter of infected horses or swine with burial or incineration of carcases under government supervision.
4)   Quarantine: Restrict movement of horses or pigs from infected farms to other areas.
5)  Immunization of contacts: Not applicable.
6)   Investigation of contacts and source of infection: Search for missed cases.
7)   Specific treatment: None at present, although there is some research evidence that ribavirin may decrease mortality from Nipah virus.
 
C. Epidemic measures:
1)   Precautions by animal handlers: protective clothing, boots, gloves, gowns, goggles and face shields; washing of hands and body parts with soap before leaving pig farms.
2)   Slaughter of infected horses or swine with burial or incineration of carcases under government supervision.
3)   Restrict movement of horses or pigs from infected farms to other areas.
 
D. Disaster implications: None
 
E. International measures: Prohibit exportation of horses or pigs and horse/pig products from infected areas.