Prof. Dr. Binod Man Shrestha
Senior Consultant Pediatrician
Animal bite is a Common problem and continuing threat to human health worldwide. It is still a major public health problem particularly in the Terai and inner Terai region of Nepal. Animal bites cause either direct injury or secondary damage due to super-added infection. Among the animal bites dog bites are the most common. Rabies (Gk “Rabbhas” meaning “to do violence”) is a fatal complication of animal bite. Children are bitten more often than adults. 30-60 % of dog-bite victims are children <15yr. Common types of mammalian/animal bites are:
- Dogs – 85 to 90 % (vast majority)
- Cats – 5 to 10 %
- Rodents – 2 to 3 %
- Farm animals (cattle/buffalo)
Majority of animal bites occur in children aged 5-10 years (45% in Lumbini Zonal Hospital study-
- 2002, and 63% in Kanti Children’s Hospital study-2016). Boys have been observed to be bitten twice more frequently than girls. OPD based Incidence of animal bites is approximately 9 % (722 / 8385).
- Lumbini Zonal Hospital study in 2002 showed dog bites in 94 % of cases. In Nepal animal bites are encountered highest (17%) in the month of Mangsir (November-December),and lowest(5%) in Ashadh (June-July)
III. Clinical profile
- Most common sites are head and neck up to the age of 10 years.
- Approximately 65% of attacks occur around home.
- 50% of bites are unprovoked.
- Dog bites rarely cause death.
- Dog bite injuries are in the form of scratches, abrasions, puncture wounds, lacerations with/out tissue avulsion, and crush injury(sometimes)
- Children are the most common victims.
- These are Common in preschool and early school-age children in daycare or preschool settings.
- Human bites occur usually as a result of aggressive play with another child.
- These are highest among adolescents (fist-to-tooth injuries or fight bites) in some series.
- These are typically located on the face, upper extremities, or trunk (chest or abdomen).
- Human bite injuries are in the form of occlusion injury and clenched-fist injury
- Cats can cause wounds with their teeth or claws.
- Two third of cat bites involve the upper extremities
- Scratches occur on the upper extremities or face
- Rats cause the majority of rodent bites.
- Most bites occur at night on the face or hands in children < 5 yrs.
- Cat and rat bites lead to deep puncture wounds penetrating the tissues because of their long,
Slender and sharp teeth.
- Infection (soft tissue bacterial) is the most common complication
Cat bite causes Cat scratch disease and occasionally osteomyelitis or septic arthritis
- Rodent bite causes Rat bite fever (very rare)
- Rabbit bite causes Tularemia
- Human bite causes Hepatitis B and HIV infections
- It is necessary to do both anaerobic and aerobic bacterial cultures of wound specimen
Higher risk of infection are for human or cat bite wounds, deep puncture wounds, if delay in treatment, immune-compromised patients, penetration of bone/tendons and if bites to hand, foot, or genitals.
- Rabies is the most feared complication of an animal bite.
- Transmission of Rabies
- Rabies viruses are excreted through body-fluids like saliva.
Vectors/ Reservoirs of rabies are Dogs, vampire bats, cats, monkeys, skunks, foxes, jackals, cattles, livestock, mongooses.
Modes of transmission:
- Animals to human
- by bites
- by scratches
- by Licks on abraded skin or mucosa
- Inhalation /aerosols in caves (excreta of vampire bats) and in laboratories
- Oral by drinking unboiled milk and eating improperly cooked meat
- Human-to-human: – Organ transplants, bite by human and Kissing (rarely)
- Pathogenesis of Rabies
Exposureà Inoculationà Virus-Host interactionà Implantation/Multiplication either in neurons or in muscles àCNS àencephalitisà Nerves à Salivary glands
VII. Diagnosis of Rabies
Clinical :- H/O of exposure to rabid animal.
IP– 2 months( 3 weeks- 3months to > 3 yrs)
- Prodromal : Pain, Par aesthesia, P (also Headache, fever, and restlessness)
- Neurological : Hydrophobia, Aerophobia, ( 80-90%):
- Brain biopsy- Negri bodies (Sellar’s stain) are pathognomonic
- Rapid Rabies Enzyme Immuno-diagnosis.
- Neutralising antibodies in serum/CSF(detected after 8 d).
Basic principles of managing animal bite wound/s:
- Assessment of severity of wound/s.
- Other therapeutic measures.
- Safety tips
- Wound toilet/cleansing (Primary deal) : It is the cheapest & most important preventive step. It can be easily done anywhere, and provides more than 60% protection. Wound should be thoroughly cleansed with soap and water (large amount) or saline and disinfected with 1% povidone iodine. Visible dirt, if present should be removed. Pressure to the wound should be exerted with a clean towel or gauze to slow or stop the bleeding, if present. X-ray may be needed to rule out bone fracture or foreign body.
- Immediate suturing (after the wound is thoroughly cleaned with povidone iodine) should be done for open laceration & facial wounds to avoid developing a scar.
- Delayed suturing is recommended for:
- Wounds at high risk of becoming infected
- Crush injuries
- Puncture wounds
- Bites involving the hands
- Dog bite wounds that occurred many hours earlier (8h)
- Cat or human bites, except those to the face
- Bite wounds in immuno-compromised children
- Assessment of severity of wound/s (WHO) :
Category I : Licks on intact skin, no mm exposure à No treatment
Category II : superficial scratches, abrasions à ARV
(no bleeding) ; licks on broken skin. (full course)
Category III: Single or multiple trans-dermal bites à ARV + RIG (with bleeding) ; Licks on mm
- Passive (for category III bite wound and immuno- compromised children).
- Equine RIG (Dose =40iu/kg;1ml=300 units)
- Human RIG (Dose =20iu/kg;1ml=150 units)
*RIG should be given intramuscularly (never intravenously) within 72 hours (max 7 days) and infiltrated into the wound.
Active immunization (for category II bite).
- Nerve tissue vaccine- 1st generation. No more used these days
- Tissue/ cell culture vaccine (TCV) – 2nd generation. These are used these days
- Purified chick embryo cell vaccine
- Purified Vero cell vaccine
- Human diploid cell vaccine
- Newer vaccines (Recombinant Vaccines) – 3rd generation:
III. Synthetic peptides
- Edible DNA vaccines
- Pre-exposure prophylaxis (PEP) :
Dose schedule (TCV): Days 0, 7 & 21/28
Indications: Veterinary persons, Laboratory workers, Postmen, Animal handlers, Hunters, Morning walkers, and Health workers (Particularly those involved in treating rabies and Patients’ attendants.
- Vaccine protocol for post-exposure treatment (PET)
- Immunized: on 0, 3, 7, 14 & 28/30 days IM in deltoid muscle
- Non –immunized: 0, 3, 7 & 28 days, 0.1 ml of vaccine ID at 2 sites
- Previously immunized: 0 & 3 days IM and no RIG is needed
* all reconstituted vaccines should be refrigerated at 2-8 C
Indications of doubling the 1st dose of TCV:
- Underlying chronic diseases.
- Immunodeficiency states: HIV/AIDS
- Use of immunosuppressive drugs.
- Severe PEM
- Delay in the t/t of bite wound of >48 hrs
- Category III bite wound/s , if RIG is not available (not substitute)
4. Other therapeutic measures
Tetanus toxoid vaccine, or Tetanus immune globulin ( if the person is not sure of the date of the last tetanus immunization).
- Antibiotics/Antimicrobials are indicated in wounds on face, hands & feet, wounds involving a bone or joint, wounds in children with immuno-suppression or diabetes (which could increase the risk of serious infection), deep human & cat bites wound, bites more than 8 hours old with oedema, and crush injury. Empiric antibiotic of choice is Amoxicillin clavulanate (either iv or oral) depending upon the severity of wound.
Treatment failure (for preventing Rabies) occurs if there is:
- Use of impotent vaccine.
- Faulty transport and storage.
- Incomplete dissolution of vaccine or under-dosing.
- Delay in starting treatment.
- Wrong categorization of woundà inappropriate T/T.
- Improper management of bite wound.
- Ignoring underlying chronic conditions.
- Use of immunosuppressive drugs.
- Unknown cause.
5. Safety tips to prevent dog bites:
- Do not approach a stray or unfamiliar dog, especially if its owner is not present.
- Do not approach a dog quickly. Allow time for the dog to acknowledge your presence before petting it.
- If a confrontation occurs, do not make eye contact and do not run or scream.
- Do not approach an unfamiliar dog while it is eating, sleeping, or caring for puppies.
- Do not leave young children or infants unsupervised with a dog.
Children having animal bites should see a healthcare provider in the following situations:
- Bleeding from bite-wound does not stop even after applying pressure for 15 minutes(indicating fractured bone or other serious injury).
- Bite on the hand, foot or head
- A bite victim has diabetes, liver disease, cancer, HIV infection, or is on immuno-suppressive medications.
- Evidence of infection in the bite-wound
- Concern about possible rabies
- Last shot of tetanus immunization more than 5 yrs
- WHO Expert Committee on Rabies, 8th report. Geneva: WHO, 1992;Technical Report Series 824.
- Wilde H. Rabies. International Journal of Infectious Diseases 1997; 1(3).
- Jacob John T, Vaccine 1997, Vol 15, Suppl .
- WHO Recommendations on Rabies Post-Exposure Treatment.
- Bhatia RK, Ichpujani RL: Rabies-a killer disease. 1994 .
- Park K. Park’s textbook of preventive and social medicine.2007; 19th edition.
- WHO expert consultation on rabies.2005. TRS 931.
- Wilde H. Failure of post-exposure rabies prophylaxis. Vaccine 2007; 25(44): 7605-9.
- Shayam C et al. Post-exposure Prophylaxis for rabies. JIACM 2006; 7(1): 39-46.
- Lodmell DL, et al. Vaccine 2000; 18. 1059-66.
- Tacket CO, Mason HS. Microbs Infect 1999;10;777-83.
- Sudarshan MK. Rabies prevention. A medical guide book. First edition; 2004.
- Patient information: Animal bites (Beyond the Basics) by Larry M B.