Infectious Diseases

CONTENT:

Bacterial Endospores

Streptococcus zooepidemicus

Toxoplasma gondii & pregnancy

Parasitic Pneumonitis

Brucellosis Impact and Management in Cattle Health

Echinococcus Granulosus in Sheep

Pseudorabies in Pigs

Ready to practice?

Click here for BCSE test sample questions

Bacterial Endospores

Several environmental factors affecting the growth and survival of bacteria, temperature is one of them. Some bacteria develop sporulation strategies to ensure survival during adverse environmental conditions such as nutrient limitation, heat, and desiccation.

After the process of sporulation, bacterial endospores remain in a dormant, metabolically inert state. The endospores are simplified forms of bacteria, consisting of the DNA genome, some small amount of cytoplasm and all have high, but very wide-ranging, resistance to heat, radiation and another harsh external conditions. The resistance of endospores is attributed to their layered structure, their dehydrated state, their negligible metabolic activity, their high levels of small acid-soluble proteins and their high content of dipicolinic acid.

The genera of bacteria that contain endospore-forming species are Bacillus (Bacillus anthracis - Antrax) and Clostridium spp (botulism, tetanus, etc.).

References:

Cristopher K. Cote. Molecular Microbiology. 2nd ed. 2015
P J Quinn. Veterinary Microbiology and Microbial Disease. 2nd ed. Wiley-Blackwell. 2011.

Toxoplasma gondii & Pregnancy

Toxoplasma & Pregnancy

Toxoplasma gondii, an obligatory intracellular parasite, instigates worldwide toxoplasmosis in humans and warm-blooded creatures. Prevalence differs regionally. Notable risk factors encompass food type, cooking methods, water treatment, and cat interaction, particularly for immunocompromised individuals. T. gondii's lifecycle encompasses final hosts (mostly cats) and intermediate hosts (humans, dogs, etc.). Infection in intermediate hosts stems from consuming undercooked meat or contaminated food with oocytes expelled by cats. This understanding is pivotal in managing the spread and impact of this parasite-linked disease.

Toxoplasma gondii, an obligate intracellular protozoan, completes its lifecycle within cats, acting as definitive hosts. Infection occurs through consumption of rodents carrying bradyzoites. Cats shed oocysts for about 1-2 weeks post-infection, with sporulation taking over 24 hours. An IgM titer ≥1:64 indicates recent infection, posing oocyst shedding risk. Owners with prior exposure might exhibit immunity, protecting against infection during pregnancy.

For T. gondii, a coccidian protozoon, cats serve as sexual phase hosts, while warm-blooded vertebrates, including humans, act as intermediate hosts. Transmission routes include meat-borne bradyzoites and cat feces-borne oocysts. Cats shed oocysts for 7-21 days, potentially leading to severe disease. Sporozoites from oocysts infiltrate and replicate in organs, muscles, and nervous systems.

Toxoplasmosis epidemiology unveils widespread T. gondii exposure in cat populations, with up to 74% seroprevalence globally. Dogs also exhibit high exposure (30%-64% seroprevalence). Often asymptomatic, infections become chronic. Cats contract the infection through rodents, driven by altered rodent behavior due to T. gondii. This zoonotic infection poses risks for humans, causing diverse serious conditions.

Preventing T. gondii involves restricting hunting and feeding cats and dogs undercooked meats. Cockroach control is crucial, and daily litterbox cleaning minimizes oocyst transmission.

In immunocompetent individuals, primary T. gondii infection induces fever, malaise, and lymphadenopathy. Maternal infection during gestation can result in stillbirth, CNS, and ocular diseases. Around 10% of AIDS patients develop toxoplasmic encephalitis from bradyzoite reactivation. The correlation between T. gondii and behavioral/mental issues varies. Tissue persistence underscores the significance of avoidance. Humans contract toxoplasmosis through oocysts, tissue cysts, or transplacentally. Prevention involves evading undercooked meats and sporulated oocysts.

Toxoplasmosis is frequently asymptomatic in humans, but it can be severe in congenital or postnatal infections. Most critical during the first trimester, congenital cases can lead to neurological and ocular issues. Generally latent, toxoplasmosis might manifest with non-specific clinical signs.

Severe effects impact immunocompromised individuals and pregnant women. Neonate cats, geriatric, and immunocompromised animals experience chronic illness and clinical symptoms.

Serological tests (direct agglutination, latex agglutination, ELISA) detect antibodies. PCR offers better sensitivity and specificity. A study identified T. gondii DNA in milk samples from goats, sheep, and cows in select countries.

Risk factors for T. gondii include poor education, with odds decreasing by 83% and 98% for low- and high-educated women, respectively, compared to illiterate women.

A higher rate of T. gondii infection occurred among employed pregnant women, potentially linked to specific occupations and associated risks. Hygiene practices revealed raw meat consumption elevated infection risk compared to cooked meat. Drinking raw milk posed a higher risk than pasteurized milk.

Contact with cats, the oocyst-spreading hosts, saw interactions with stray and pet cats linked to infection. No direct connection between ownership and infection was observed. Handwashing after cat contact reduced infection risks due to fecal-oral transmission. The high prevalence attributed to rural residence, cat contact, and poor hygiene compliance among participants.

Poor education, occupation, raw milk consumption, contact with cats without appropriate hygienic practices, and undercooked meat eating linked to T. gondii infections.

Urgent handwashing awareness campaigns are crucial for public health. Cat owners, especially pregnant women, should be aware of T. gondii infection risks and adopt appropriate hygienic practices.

REFERENCES:

Hassanen, EAA. Interplay between cross sectional analysis of risk factors associated with Toxoplasma gondii infection in pregnant woman and their domestic cats. Frontiers in Veterinary Science. 2023.
Bruyette, DS. Clinical Small Animal Internal Medicine. Wiley Blackwell. 2020.
Sykes, JE. Greene’s Infectious Diseases of the Dog and Cat. 5th ed. Elsevier. 2023

Do you have any feedback about the Quick Note?

We'd love to hear from you!

Feel free to send us a message

Don't forget to share with any friends who are also

preparing for the BCSE Exam.

Parasitic Pneumonitis

Parasitic Pneumonitis, caused by Parascaris equorum or Dictyocaulus arnfieldi, affects foals and horses, with respiratory signs like exercise intolerance and coughing. P. equorum typically infects foals early in life orally, migrating through the liver and lungs en route to the gastrointestinal tract, leading to verminous pneumonia and "summer colds." Gastrointestinal infection may cause unthriftiness, colic, obstruction, or perforation. Due to widespread persistent environmental contamination and the ability of this parasite to cause pathology during its prepatent period, it is important to preemptively treat foals at risk for infection.

Parasitic Pneumonitis is a condition that can affect foals and adult horses, caused by Parascaris equorum or adults of Dictyocaulus arnfieldi. Clinical signs include exercise intolerance, coughing, nasal discharge, fever, and depression, especially in cases of secondary bacterial infection. P. equorum is common in foals, while D. arnfieldi affects horses of any age, requiring a donkey as a primary host to complete its life cycle.

Clinical Findings:

Foals with parasitic pneumonia exhibit chronic coughing, mucoid or mucopurulent nasal discharge, respiratory distress, and poor body condition. Auscultation reveals abnormal lung sounds and crackles. Signs of intestinal infection such as colic may also be present.

Diagnosis:

Hematological tests show an inflammatory response with mature neutrophilia, hyperfibrinogenemia, and hyperglobulinemia. Thoracic radiography and ultrasound are useful for diagnosis. Cytological analysis of tracheobronchial aspirate reveals eosinophilia. Fecal flotation detects parasite eggs.

Treatment:

Severely hypoxemic patients may require oxygen. Fenbendazole (5 mg/kg) is used to treat P. equorum, with the dose increased to 10 mg/kg after 24 hours if there are no complications. Pyrantel pamoate (6.6 mg/kg) or ivermectin (200 μg/kg) can also be used. D. arnfieldi is treated with ivermectin or moxidectin in adult horses.

Prognosis:

Recovery is excellent with proper treatment. Emphasis is placed on the need for thorough deworming, including donkeys and mules, as they are a source of environmental contamination.

References:

Reed, SM. Equine Internal Medicine. Elsevier. 4th ed. 2018.
Sellon, DC. Equine Infectious Diseases. Elsevier. 2nd ed. 2014.
Zachary, JF. Pathologic Basis of Veterinary Disease. 6th ed. Elsevier. 2017.

Brucellosis Impact and Management in Cattle Health

Brucellosis

Brucellosis in cattle, notably caused by Brucella abortus, is a significant veterinary concern due to its impact on reproductive health, leading to abortions typically in the latter half of gestation. Contrary to a common misconception, affected cows usually experience this adverse outcome once, with subsequent pregnancies often proceeding normally. This condition not only affects cattle but also spans across various domestic animals, including pigs, which are susceptible to Brucella suis.

Diagnosis hinges on serological testing, with serum agglutination at specific dilutions indicating positive reactors, taking into account the vaccination status of the animal. The Brucella milk ring test, while useful, can yield high false positives, necessitating careful interpretation of results.

There is no effective treatment for brucellosis; hence, control measures focus on herd testing, culling of infected animals, and vaccination strategies employing strains like 19 or RB51 to bolster resistance within the herd. The approach to managing this disease is primarily preventive, aiming to curb its spread and mitigate its impact on animal health and productivity. Additionally, brucellosis poses zoonotic risks, underlining the importance of rigorous disease management and biosecurity practices to protect both animal and human health.

Diagnostic tests for brucellosis in cattle primarily involve serological assays like the Milk Ring Test for bulk milk samples, and the Rose Bengal Plate Test, ELISA, or Complement Fixation Test for individual animals. Positive results indicate exposure to Brucella bacteria but require further testing for confirmation due to possible false positives. The bacterial isolation from milk, blood, or tissues offers a definitive diagnosis. Interpretation of results must consider the test's sensitivity and specificity, along with the animal's history and clinical signs.

A profound comprehension of brucellosis’ epidemiology, diagnostic approaches, and preventive strategies is imperative for optimizing herd health management and safeguarding public health. This encompasses understanding the specific dilutions for serological tests—1:100 for unvaccinated and 1:200 for vaccinated animals as indicative of a positive reaction—and the critical evaluation of diagnostic results against the backdrop of the animal’s clinical history and symptomatology.

REFERENCES:
Merck Veterinary Manual. Brucellosis in Cattle.

Do you have any feedback about the Quick Note?

We'd love to hear from you!

Feel free to send us a message

Don't forget to share with any friends who are also

preparing for the BCSE Exam.

Echinococcus Granulosus in Sheep: Diagnosis and Management

Echinococcus

Echinococcus granulosus causes Cystic Hydatid Disease in sheep, with canids as primary hosts and sheep as intermediate hosts. In sheep, clinical signs depend on infection intensity, cyst size, and location, potentially leading to poor body condition and respiratory distress due to lung cysts. Diagnosis involves fecal exams or necropsy, identifying hydatid cysts in organs, especially the liver or lungs. Management includes controlling the parasite in canid populations, as direct treatment in intermediate hosts like sheep is impractical.

REFERENCES:

Cornel Wildlife Health Lab. Echinococcosis.

Do you have any feedback about the Quick Note?

We'd love to hear from you!

Feel free to send us a message

Don't forget to share with any friends who are also

preparing for the BCSE Exam.

Pseudorabies Pigs

Pseudorabies in Pigs

Pseudorabies, caused by a DNA herpesvirus, primarily affects swine but can also incidentally infect other species. The virus spreads through direct contact, such as nose-to-nose or fecal-oral transmission, and indirectly through aerosolized particles. It can survive in various environments, including nonchlorinated water, soil, and feces. Clinically, young piglets often present with central nervous system (CNS) disease and have high mortality rates, while weaned pigs typically show respiratory disease. General signs across affected pigs include fever, anorexia, weight loss, sneezing, and dyspnea. In nonporcine species, the infection can cause sudden death, pruritus, CNS signs, and fever. The virus replicates in the nasal, pharyngeal, or tonsillar epithelium and spreads to the brain via lymphatics and nervous tissue. Diagnosis is based on reproductive failure and CNS signs in piglets, confirmed through serology, PCR, or virus isolation. Although there is no specific treatment, vaccination is highly effective and critical for control, contributing to the successful eradication of pseudorabies in the USA’s commercial pig industry.

References:

Merck Veterinary Manual. Pseudorabies in Pigs.

Do you have any feedback about the Quick Note?

We'd love to hear from you!

Feel free to send us a message

Don't forget to share with any friends who are also

preparing for the BCSE Exam.

Sample Questions

BCSE Test Sample Questions

1. Which of the following is the primary method of transmission for pseudorabies in swine?
A) Vector-borne transmission
B) Direct nose-to-nose or fecal-oral contact
C) Vertical transmission from sow to piglet
D) Fomite transmission only

2. Which clinical sign is most commonly associated with pseudorabies in young piglets?
A) Diarrhea
B) Severe pruritus
C) Central nervous system (CNS) disease with high mortality
D) Chronic cough

Share our BCSE test sample questions with your fellow test-takers.

Answers and Explanation

Question 1:

Answer: B) Direct nose-to-nose or fecal-oral contact

Explanation: Pseudorabies is primarily transmitted through direct contact, specifically via nose-to-nose or fecal-oral routes. This mode of transmission allows the virus to spread efficiently among swine populations, contributing to the disease's persistence in infected herds.

Question 2:

Answer: C) Central nervous system (CNS) disease with high mortality

Explanation: In young piglets, pseudorabies often manifests as severe CNS disease, leading to high mortality rates. This is a distinguishing clinical feature of the disease in this age group, in contrast to older pigs, where respiratory signs are more common.