|
|
|
|
|
|
|  |  |  |
Home / Case studies / #07
Case study #07
 |
 |
 |
 |
On a Friday morning in the middle of June, you receive a call from the owner of a cattle farm for which you are the veterinarian. The farm has 95 dairy cows with access to pastures. The owner explains that this morning they found 3 dead animals, 2 of which showed no clinical signs and the remaining animal had hemorrhages in the nostrils. On the same farm, they also have 8 horses that graze freely in the area, one of which was found dead with symptoms of bloat and the skin around natural openings stained with a bloody exudate.
Figure 1: A dairy cattle farm in which the animals have access to pastures
that animals share with horses from the same farm and other animals.
Given the severity of the condition, you urgently decide to create a list of differential diagnoses for diseases that acutely present with bleeding and animal death, adhering to the current legislation which mandates reporting to the official Veterinary Services. Considering the zoonotic risk, spread, etc., the Veterinary Services Office (VSO) implement appropriate biosecurity measures according to the surveillance and control program in accordance with applicable legislation.
Considering the risk of dissemination, necropsy of the animal will not be performed. Samples are sent to the Central Laboratory of Animal Health - Santa Fe (Granada), which has the appropriate BSL3 facilities to handle the samples.
Figure 2: Appearance (10X) of colony-forming units of bacteria grown in PEA medium
for 48h at 37ºC (source: https://phil.cdc.gov/Details.aspx?pid=17081)
Figure 3: Microscopic image of Gram-positive endospore-forming bacilli
(source: https://phil.cdc.gov/Details.aspx?pid=9826)
In the BSL3 laboratory, they perform a blood agar culture where white colonies grow ranging from 2 to 5 mm in size, with a dry appearance, irregular borders, and no hemolysis. The Gram stain shows large, straight, gram-positive bacilli with the presence of spores.
Figure 4: Timpanized horse, skin stained with bloody exudates from natural openings
(source: Sofía Gabriela Zurita, Hospital Clínico Veterinario, Universidad de Extremadura)
Secondary questions
|
 |
 |
Main question
What could be the pathogen causing this process?
- Epizootic hemorrhagic disease virus
- Bacillus anthracis
- Crimean-Congo haemorrhagic fever virus
- Clostridium chauvoei
Solution
|
 |
The identified pathogen was Bacillus anthracis.
This is the etiological agent of bacterial anthrax, malignant anthrax, or anthrax. This pathology affects various animal species (mammals and some birds), being especially severe in herbivores (both domestic and wild). It is a disease of worldwide distribution and is included in the list of diseases that must be reported to the World Organization for Animal Health (WOAH). B. anthracis is a gram-positive bacillus whose infectious form is the spore. This resistant form persists for long periods of time in the soil, causing disease outbreaks, for example, when ingested by ruminants on contaminated pastures. Upon entering a susceptible host, the bacteria produce toxins that lead to the typical disease symptoms. This bacterium is zoonotic with various patterns: cutaneous, gastrointestinal, and inhalational, which can result in a fatal outcome.
It is a biosafety level 3 pathogen. There are different approaches for the diagnosis of B. anthracis. For example, bacterial culture on blood agar supplemented with 5-7% horse/sheep blood and selective medium and subsequent identification of the isolates by PCR.
In animals, the characteristics of the disease vary according to the affected species. For example, in cattle, it usually presents an acute or hyperacute form with sudden deaths or symptoms such as hemorrhages in mucous membranes, among others. In the case of horses, with a typically acute for, digestive disorders, fever, and colic can occur, among other symptoms.
The surveillance and control program for bacterial anthrax in Spain, under Regulation 689/2020, establishes a system of passive surveillance based on the mandatory reporting of any suspected case of bacterial anthrax in the listed species. More information can be found on the website of the Ministry of Agriculture, Fisheries and Food of the Government of Spain, the World Organization for Animal Health, and the European Food Safety Authority.
