1. Rhabdoviridae

2. Rhabdoviridae Bullet-shaped RNA viruse
Rhabdoviridae encompasses more than 175 viruses of
vertebrates, invertebrates, and plants.
Most famous member is rabies virus.
It causes one of the oldest and most feared disease

3. Rhabdoviridae Medium size 70 nm in diameter and 170 nm long
Enveloped with large peplomers
Helical cylindrical nucleocapsid-giving the virus the bullet (conical) shape
Non segmented single-stranded negative-sense RNA
Genome is encoding 5 genes.

5. Structure and genomic organization of Rhabdovirus (VSV)
[Principles of Virology, 2000-ASM Press, Washington DC]
Structure and genomic organization of Rhabdovirus (VSV)

6. Rhabdoviridae Classification
Four genera
Lyssavirus is the most important genus.
Rabdovirus has different serotypes
Each of these viruses is considered capable of causing rabies-like disease in animals and humans

7. What is a Fixed Virus
One whose virulence and incubation period have been stabilized by serial passage and remained fixed during further transmission.
Rabies virus that has undergone serial passage through rabbits, thus stabilizing its virulence and incubation period and called as fixed virus

8. Electron Micrographs of Animal Rhabdoviruses
Batvirus - negri bodies brain
VSV- ocassional elongated form of virion
Bovine ephemeral fever virus
Sawgrass virus –isolated from tick-unassigned
Figure 39-1 Electron Micrographs of selected animal rhabdoviruses. A: Lyssavirus, Lagos bat virus. A typical Negri body (N) in the brain, with budding virions (*42,000). B: Vesiculovirus, vesicular stomatitis virus. Occasional anomalous elongated form of the virus (*35,000). C: Ephemerovirus, bovine ephemeral fever virus. Isolated from a cow in Australia, Late infection of VERO cell (*110,000). D: Unassigned, sawgrass virus. Isolated from a tick in Florida (*137,500). (Photographs courtesy of Sylvia Whitfield, CDC, NCID, DVRD, VRZB.)

9. RABIES VIRUS (RV)

10. Epidemiology
Rabies can infect all warm-blooded animals, and in nearly all animals, the infection is fatal.
Dogs are the most important source of human rabies infection.
Disease is worldwide, except Japan, United Kingdom, Antarctica, Hawaii and some Caribbean islands.

12. Epidemiology Bat Rabies in USA
Worldwide, 40,000 to 50,000 people die of rabies/year approx 10 million receive post-exposure treatment.
Bats in USA and Europe is the source of most human rabies cases. In many cases there is no history of bite.

13. RV Pathogenesis Transmitted by bite or scratch from a rabid animal.
However, in bat caves the infectious virus concentration may be high resulting in aerosol transmission.
Incubation period: 14 to 90 days (in humans can be more than 2 years after exposure).

14. Development of overt rabies depends on:
Rabies as a CNS disease
Development of overt rabies depends on:
(a) Location of the bite – virus must enter the peripheral nerves to travel to brain
(b) Severity of bite
(c) Species of animal involved (E.g. foxes carry up to 106 infectious particles of rabies virus/ml of saliva)

16. RV Pathogenesis
RV enters peripheral nerves through sensory and motor nerve endings – primarily through neurotransmitter acetylcholine as receptor. Also uses gangliosides and phospholipids.

17. Sequential event following Rabies virus infection in a dog

18. RV Pathogenesis
Virus enters the brain through the limbic system where it replicates extensively – affecting the cortical control of behavior and leading to the furious form of disease.
As the virus continues to spread within the CNS, it reaches the neocortex – resulting in change in clinical disease from fury to dumb or paralytic form.

19. RV Pathogenesis
Virus moves centrifugally from the CNS through the peripheral
nerves to:
Adrenal cortex
Pancreas
Salivary glands
Virus release
In CNS, virus is released from cells by budding into
intracytoplasmic membrane. However, in the salivary glands,
the virus buds at the apical surface of mucous cells resulting
in release of large amounts of virus in saliva. By the
time when furious form of disease is evident and animals bite
indiscriminately, the saliva is highly infectious.

20. Clinical disease
There is a prodromal (warning) phase before clinical disease that is characterized by change in temperament.
NOTE: Higher proportion of dogs, cats, and horses exhibit the furious form than ruminants and lab animals.

21. Rabies clinical forms: Furious and dumb (paralytic)
Furious form – Animal is restless, nervous, aggressive, and dangerous (fearless). Inability to swallow water (hydrophobia), excessive salivation, exaggerated response to light and sound, hyperesthesia (animals commonly bite or scratch themselves).
Dumb or paralytic form - As encephalitis progresses, fury gives way to paralysis. Convulsive seizures, depression, coma, and respiratory arrest resulting in death 2 to 14 days after onset of clinical signs.

23. Majority will succumb to Disease

26. Rabid dog 4 days after
developing clinical signs.
Rough hair coat,
exudates in the eyes,
contracted pupils.
Dog paralysed for 4 hr
and died 8 hr later

27. Rabid dog - marked mandibular paralysis

28. Rabid African ox (furious
form)
Excessive salivation and
loss of body condition (top)
Excessive salivation
continued until death
(below)

29. Control and prevention
Developed countries
Stray dog and cat removal and control of movement of pets
Immunization of dogs and cats
Routine laboratory diagnosis to obtain accurate incidence data
Surveillance to assess the effectiveness of all control measures
Public education to ensure cooperation
Vaccines
Inactivated and attenuated RV vaccines are efficacious and safe in animals.

30. If you are bitten or scratched
Tell an health care worker immediately
Wash the wound out with soap and water
Inform the doctor right away

31. POSTEXPOSURE PROPHYLAXIS
Wound cleaning & treatment

34. prevention No effective treatment exists.
Postexposure Prophylaxis/PEP: 3 steps
1. Wound care: immediate thorough washing with soap and water and a virucidal agent such as povidine-iodine or 1-2% benzalkonium chloride.
Shown to be protective if performed within 3 hours of exposure
If puncture, swab deeply in wound and around edges

35. PREVENTION
2. Passive Immunization: Human rabies immunoglobulin (HRIG) 20 IU/kg ASAP, but not longer than 7 days after vaccine given. Infiltrate entire dose around wound, any remaining IG inject IM at a site distant from the vaccine.
3. Human diploid cell vaccine (HDCV): 1 ml (deltoid) on days 0,3,7,14,28. do not give in gluteal. If injected into fat, no antibodies formed.

36. PREVENTION
(HRIG and HDCV: give in different anatomical sites and never in the same syringe.
If previously vaccinated - no rabies Ig + vaccine at 0, 3 days only)

37. Guides to Human Post-exposure Prophylaxis
Dog, cats Healthy and available for observation None -
Rabid or suspected Rabies Ig + vaccine
Unknown Consult PH official
Bat Regard as rabid and consider that exposure Rabies Ig + vaccine
occurred even if a bite wound is not
evident. Unless lab results negative
Skunk, fox, coyote Regard as rabid unless proven Rabies Ig + vaccine
Bobcat, woodchuck, negative
other carnivores
Livestock, rodents, Case by case-judgment call
rabbits, hares

38. PREVENTION Pre-exposure vaccination Veterinarians
Lab workers working with RV
wildlife workers in endemic areas
Pre-exposure vaccination regime – 0, 7, 28 days
PREVENTION

39. Lab Diagnosis كشتن حيوان مشكوك به هاري و ارسال سر حيوان
به انستيتو پاستور( بريدن سر حيوان بايد بوسيله
مامورين دامپزشكي يا بهداشت با استفاد هاز
وسائل كامل خفاظتي انجام مي گيرد و در يك كيسه نايلوني
ضخيم غير قابل نفوذقرار داده و آن را در يك يخدان
پر از يخ قرار مي دهند ).
نمونه برداري از بافت مغز با استفاد ه از
كيت هاي مخصوص نمونه برداري.

40. The standard premortem test is a fluorescent antibody test to demonstrate the presence of viral antigen. The standard postmortem test is biopsy of the patient's brain and examination for Negri bodies. Autopsies are rarely performed.

41. Lab Diagnosis
1. Immunofluorescence - Suspected animals must be killed and brain tissues collected for testing. Diagnosed by direct
immunofluorescence showing RV antigens in medulla, cerebellum, or hippocampus.- observe Negri
bodies in neurons.
2. RT-PCR – test for RV-RNA in brain
3. Antemortem diagnosis – only done in suspect human cases. Skin biopsy, corneal impressions, or saliva specimens are used.
Only positive results are significant in this method because negative results could be due to the fact that these
negative results could be due to the fact that these samples are not optimal.

42. Negri bodies – A gold standard in Diagnosis
Inclusion bodies called Negri bodies are 100% diagnostic for rabies infection, but found only in 20% of cases

43. Negri bodies in Brain Tissue
Negri bodies  round or oval inclusion bodies seen in the cytoplasm and sometimes in the processes of neurons of rabid animals after death.
Negri bodies are Eosinophilic, sharply outlined, pathognomonic inclusion bodies (2-10 µm in diameter) found in the cytoplasm of certain nerve ..

44. Light microscopic photograph of multiple
intracytoplasmic rabies virus inclusions in a neuron
from the brain of a naturally infected bison
Light microscopic photograph of multiple intracytoplasmic rabies virus inclusions in a neuron from the brain of a naturally infected bison, revealed by immunohistochemistry (*400). (Photograph courtesy of Michael Niezgoda, CDC, NCID, DVRD, VRZB.)

45. Negri bodies – collection of RV nuclocapsids in neurons
Pathogenesis of rabies virus