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Case study #02

Zoono-tic Case post Zoono-tic Intro reel Zoono-tic Clue 02 Zoono-tic Clue 02

Several dogs picked up on public roads arrive at the Animal Protection Center where you work. One of them comes from the street, since its owner was taken to the hospital. At the first inspection of the animals, all are healthy, and the vaccination protocol established at the center is carried out. On the third day, it is observed that the defenseless animal has strange behavior: it has barely eaten, drools excessively and is very aggressive, attacking anyone who approaches. The next day, in the routine check of all the animals, the animal appears dead.

Video 1: Animal in the kennel of the animal protection center (source: Juan Carlos Ortiz, AVEM)

Post-mortem examination of the animal revealed macroscopically a congestion of the brain and histologically the presence of Negri bodies.

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Image 1: Brain congestion (source: David Sardón, Anatomopatólog)

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Image 2: Photomicroograph of a hematoxylin-eosin (H&E) stained brain tissue. Negri bodies (source: CDC Public Health Image Library (PHIL))

The lesions observed in the brain raise suspicion of a viral process and the following differential diagnosis is proposed:

  1. Aujeszky’s disease
  2. Rabies

The brain tissue is sent to the Carlos III Health Institute for antigen detection by the direct immunofluorescence method, where the presence of viral antigens of the agent responsible for the process is confirmed.

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Image 3: Using a direct fluorescent antibody (DFA) stain, this photomicrograph revealed the presence of viral antigen (source: CDC Public Health Image Library (PHIL))

Secondary questions

Zoono-tic Question 01 Zoono-tic Solution 01
Zoono-tic Question 02 Zoono-tic Solution 02

Main question

What could be the pathogen behind this outbreak?


Zoono-tic Promo Reel

The pathogen identified was the rabies virus.

Rabies is a viral zoonosis, caused by a single-stranded linear RNA type virus of the Rhabdoviridae Family and the Lyssavirus genus.

Transmission of the virus occurs mainly through the bite of a sick animal, or when its saliva comes into intimate contact with fresh, open wounds. An incubation period is estimated to be 2 to 8 weeks, sometimes as little as 10 days or even 1 year or more.

The transmissibility period of a dog sick with rabies extends from the time it begins to eliminate the virus through saliva until it dies, this period generally not exceeding 10 days. Therefore, the 14 days that Spanish legislation determines as mandatory to keep a dog under observation, counted from having bitten, are sufficient to ensure, if the animal is still alive, that it has not been able to transmit rabies. through that aggression.

Rabies is still present in the world, with two-thirds of countries still infected. Half of the world's population lives in endemic areas, and more than 80% of deaths occur in rural areas with little or no access to health information campaigns and care after a bite.

Africa and Asia are the continents with the highest risk of human mortality, with more than 95% of fatal cases in the world. Canine rabies is also less controlled in these regions.

Hosts include a large number of mammals. The dog is the main host involved, although there are other hosts depending on the geographical area, in Europe the bat (Spain), the red fox (Vulpes vulpes), and other small wild carnivores such as the raccoon dog in Central Europe are particularly important. the Baltic.

Spain has had rabies-free status by the World Organization for Animal Health (OMSA) in captive and wild animals since 1978, with the exception of the case of rabies imported from Morocco declared in June 2013. This event led to the temporary suspension during 6 months of rabies-free status before the OMSA.

Of course, the situation is different in Ceuta and Melilla, where imported cases of rabies in dogs occur sporadically, given their geographical proximity to Morocco, with the consequent risk of secondary transmission to other susceptible animals. Thus, in 2021 and 2022, outbreaks of canine rabies were reported in Ceuta and Melilla, with autochthonous transmission identified in the case of Melilla.

Given the war conflict in Ukraine, Spain developed a specific protocol of actions for the arrival of pets from Ukraine, valid until March 15, 2023 to minimize the risk of entry or spread of the virus, which updated the previous plan from 2011.