SPR L14 Vector-bourne Infections and Zoonoses Flashcards Preview

Pathology > SPR L14 Vector-bourne Infections and Zoonoses > Flashcards

Flashcards in SPR L14 Vector-bourne Infections and Zoonoses Deck (27):

Learning Outcomes

  • Describe the epidemiology, clinical effects, microbiology and treatment of Malaria.
  • Briefly describe a key arbovirus infection (Dengue)
  • Briefly describe Lyme disease.
  • Very briefly describe the filovirus viral haemorrhagic fevers.
  • Briefly describe the key zoonoses (Q fever, anthrax, plague, leptospirosis, brucellosis)

Key Conditions Covered


Define the following...

  1. Vector Bourne
  2. Zoonoses
  3. Give examples of each, and of a condition that exhibits both methods of transmission

  1. Arthropod transmission
  2. Non human animal source, Humans usually dead end host.

  3. See picture



  1. Where is it seen?
  2. Why is it on an increase globally?
  3. What percentage of the world's pop is infected?
  4. What contributes to this?
  5. How is it transmitted?

  1. Africa, India, the Far East and South America.
  2. Because of drug and insecticide resistance
  3. 35% of the world's population is infected - 10 million new cases annually and ~ 2 million deaths.
  4. Increased air travel - new cases are regularly seen in the developed world
  • Mosquito
  • blood transfusion,
  • needle accidents or,
  • mother to fetus. 



  1. What causes malaria in man?
    1. Name the species
  2. Which is the most virulent?
  3. Describe the life cycles of this infection
  4. What does this infection affect?

  1. 4 species of Plasmodium cause malaria in man (protozoan parasite)
    1. Plasmodium





  2. P. falciparum
  3. most complex life cycles of any human infection- three quite distinct stages & alternating extracellular and intracellular forms
  4. Affect RBCs 



  1. What causes malaria in man
  2. Describe each species

  1. 4 species of Plasmodium cause malaria in man (protozoan parasite)
  2. Plasmodium
    1. -falciparum







Clinical features of malaria


  • fluctuating fever and drenching sweats
  • Wide clinical spectrum from simple fever to fatal cerebral or renal disease
  • Fever follows rupture of erythrocytic schizonts and is mainly due to the induction of cytokines
  • The synchronous cycle in red cells means that the different species of malaria give characteristic patterns of fever, 48-hour periodicity for P falciparum
  • Headache, muscle pains and vomiting are common.
  • Enlargement of the spleen and liver is common and anemia almost invariable. 


Malaria - Complications

List the complications



  • cerebral malaria
  • severe anemia
  • hypoglycemia
  • lactic acidosis
  • glomerulonephritis 

Complications most common in  falciparum malaria in children aged between 6 months and 5 years, and in pregnant, women. However occur at any age in the non-immune (e.g. tourists).


Diagnosis - Malaria

  1. How is it diagnosed?
    1. What is a disadvantage?
  2. Who is investigated?
  3. Parasitemia may be asymptomatic, what does this mean for the patient?
  4. What confirms previous exposure?
  5. What would suggest a recent attack?

  1. Malaria is diagnosed by finding  parasitised red cells in a blood film
    1. can be insensitive - Other antigen detection methods are available
  2. Any case of fever, especially with anemia, splenomegaly or cerebral signs, in a patient who conceivably could have malaria is therefore best treated as malaria.  
  3. presence of parasites in the blood of an ill patient from an endemic area does not mean malaria is the cause of the illness
  4. The demonstration of antibody by immunofluorescence or ELISA confirms previous exposure
  5. predominance of IgM would suggest a recent attack. 


Treatment - Malaria

  1. What is the drug of choice for life-threatening malaria?
    1. What is this being replaced by? Why?
  2. Give examples of other drugs used?
  3. What can be done to prevent malaria?

  1. Quinine
    1. Artemisinin-based combination therapy due to resistance
  2. Other drugs
  • Cloroquine (to which P. falciparum is increasingly resistant) is mostly used for non-falciparum malaria especially vivax malaria
  • doxycycline
  • primaquine for preventing relapses.


  • bednets impregnated with mosquito repellents.
  • Other measures to reduce mosquito risk
  • Drug prophylaxis – various approaches eg doxycycline
  • No vaccine-yet 




Malaria fever charts showing cyclical fluctuations in temperature. Why?


The peaks coincide with the maturation and rupture of the intraerythrocytic schizonts, occurring every 48 hours for P falciparum


Arbovirus infection (e.g Dengue)

  1. What types of viruses are involved?
  2. What transmits these?
  3. What are the clinical features?
  4. Who is it increasingly common in?

  1. Mainly Flavivirus & Alphavirus
  2. Ticks, mosquitoes, & other arthropods
  3. Rashes, meningitis, encephalitis, hepatitis
  4.  travellers returning to UK (especially Westnile virus, Chikungunya, Dengue)  Zikavirus


Dengue virus causes Dengue fever

  1. What is the Dengue virus?
  2. How is it transmitted?
  3. Where does the virus replicate?
    1. What are the clincical features?
  4. What is the severe form of the disease?

  1. Flavivirus with 4 serotypes (DV-1 DV-2 DV-3 DV-4)
  2. transmitted by mosquitoes in tropical areas - emerging disease problem 50-100 million cases /yr.
  3. in monocytes & vascular endothelium.
    1. malaise, fever, headache, arthralgia, nausea and vomiting, and sometimes a maculopapular or erythematous rash.
  4. Dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS. - Fatality rate of 1-5%, Second infections with different serotype (SEE PICTURE)


Another arbovirus... Zikavirus

  1. How is it transmitted?
  2. What are the clincical features?

  1. Mosquito transmitted (Aedes)
  2. Mild diseases but emerging propensity to cause fetal damage => microcephaly and ery defects

PHEIC Public Health Event of International Concern


Lyme disease (or Lyme Borreliosis) 

  1. What is it caused by?
  2. How is it transmitted?
  3. What does human infection follow?
  4. What are the clinical features?
  5. When is it more common?
  6. How is a diagnosis made?
  7. What is the incubation period?

  1. Borrelia burgdorferi
  2. Transmitted by Ixodes ticks - World wide including British Isles - Reservoir typically mice and deer (–No Person-to-person transmission)
  3. bite of an infected tick (usually nymph).
  4. fever, headache, myalgia, lymphadenopathy

    site of the tick bite: skin lesion is called erythema migrans

  5. more common in summer -recreational exposure to infected ticks is more likely.
  6. By serology (antibody - ELISA)
  7. 1 week


Lyme disease (or Lyme Borreliosis) 

Lyme disease commonly causes additional disease up to 2 years after the initial illness

What additional disease can be caused?


What is the treatment? (In early and late disease)

  • neurologic
    • (meningitis, encephalitis, peripheral neuropathy)
  • arthralgia and arthritis
    • may persist for months or years. 


Doxycycline or amoxicillin -effective in treatment of early disease.

Late disease requires more aggressive therapy, e.g. intravenous penicillin or ceftriaxone for 30 days


Haemorrhagic fevers

  1. Give examples of these
  2. Where is it common?
  3. What are these caused by?
  4. What do patients develop?
  5. What is the treatment?
  6. What is the reservoir?

  1. Marburg and Ebola hemorrhagic fevers
  2. central and east Africa
  3. caused by filoviruses, long filamentous single-stranded RNA viruses.
  4. fever, hemorrhage, rash and disseminated intravascular coagulation
  5. no specific treatment and no vaccine for either virus.
  6. probably bat

Big outbreaks involving hospital transmission and HCW infection



Q fever 

  1. What is this caused by?
  2. What is inoculation mainly?
  3. What species of animals are infected?
  4. What are the clinical symptoms?
  5. When is recovery usually complete?
  6. How is the diagnosis made?
  7. What is the treatment?

  1. Coxiella burnetii - Obligate intracellular organism, Particularly common in NI (1/3rd of UK cases), resistant to desiccation, heat and sunlight
  2. Respiratory inoculation mainly (inhalation of desiccated bacteria)
  3. Key reservoir is cattle and sheep - placenta key source of infection - Unpasteurised milk
  4. fever, severe headache, and often respiratory symptoms and an atypical pneumonia. hepatitis.

  5. Recovery is usually complete in 2 weeks, but the disease can become chronic (usually endocarditis)

  6. Serology

  7. Acute infection is treated with oral tetracyclines; Chronic infections may require drug combinations



  1. Describe the causal bacteria
  2. Where is anthrax seen?
  3. In resource-rich countries, human infection is rare and has been due to...

  1. Bacillus anthracis - large Gram-positive rods, Aerobic, non-motile-has resistant spores

  2. a disease of herbivores such as sheep & cattle - Humans are relatively resistant (skin and mucous membranes, respiratory tract suspectible)

  3. exposure imported hides, skin, wool, goat hair and bristles, bones and bone-meal in fertilizers.

    –bioterrorism (USA) 2001



What are the two forms of anthrax? Describe each.


What is the treatment?

How is diagnosis made?

Cutaneous anthrax

  • Skin -black eschar, 'malignant pustule'
  • disease can be fatal if untreated
  • anthrax toxin => edema and congestion
  • lymphatic involvement leads to septicaemia in 10% of cases -Can lead to generalized toxic effects, edema and death

Pulmonary anthrax

  • pulmonary edema mediastinal hemorrhage
  • High fatality rate - rapidly fatal
  • 'woolsorter's disease'.  

penicillin, early, large doses

penicillin, early, large doses

Culture and PCR



  1. What causes this?
  2. What is the reservoir? How does bacteria spread to humans?
  3. Describe the plague historically
  4. How is it transmitted?
    1. Descibe the 'pneumonic plague' that can result?

  1. Yersinia pestis - small Gram-negative rod 
  2. rodents - Bacteria spread from animals to humans by fleas
  3. In the 14th century, about 25% of the population of Europe died due to plague - Now rare in Europe
  4. rat flea bite to human transmits 'bubonic' plague - not generally transmitted from person to person.
    1. when there is extensive replication of bacteria in the lung, with broncho-pneumonia the infection can spread from person to person by respiratory droplet spread, causing 'pneumonic' plague, -extremely rapid onset. 


Plague - Clinical

  1. What are the clinical features?
  2. What can occur if the infection isnt arrested at this stage?
  3. What are the complications?
  4. How is diagnosis made?
  5. What is the treatment?

  1. Fever, lymph nodes become tender (enlarge to form buboes, 2-6 days after flea bite)
  2. spread to the blood often occurs, with septicemia, hemorrhagic illness and multisystem involvement (spleen, liver, lungs, CNS).
  3. disseminated intravascular coagulation, pneumonia, meningitis. 
  4. Bacteria can be cultured from lymph nodes. Microscopy: staining is bipolar. 

  5. Streptomycin & tetracycline



  1. What is this caused by?
  2. What are the hosts?
  3. How does the human infection come about?

  1. Leptospira interrogans complex  - many species & serotypes , tightly coiled spirochetes
  2. Lots of different animal hosts (especially rodents)
  • ingestion of contaminated water or food.
    • enter through breaks in skin or mucosae, so infection can be acquired by swimming, working or playing in contaminated water.
    • miners, farmers, sewage workers, and water sports enthusiasts are especially at risk.

There are about 80 UK cases/year - person-to-person transmission is rare. 


Clinical features of leptospirosis

  1. What is the incubation period?
  2. What are the clinical features?
  3. What are the features of the more severe cases?
  4. How is diagnosis made?
  5. What is the treatment?

  1. incubation period of 1-2 weeks
  2. influenza-like pyrexial illness. - 90% of cases resolve uneventfully. The main clinical signs result from damage to the endothelia of blood vessels
  3. hepatitis, jaundice, Haemorrhage, meningitis

Weil's disease severe form with hemorrhagic complications and kidney and liver failure, occurs in only 5-10% of patients with leptospirosis.

4. Serology - looking for antibodies to leptospirosis (can be a delay in this - treat empiracally)

5. tetracycline (Chronic infections may require drug combinations



  1. What is it caused by?
  2. What are the 4 specials that can cause disease in humans?

  1. brucella - small Gram-negative non-motile coccobacilli, intracellular replication.
  2. Brucella abortus (Cattle - infectious placenta, vets etc infected), B. melitensis, (Sheep/Goat), B. suis (Pigs) B. canis (Dogs)

In cows & goats, brucellae localise in the placenta & cause contagious abortion also shed for long periods in milk. 

Big outbreak in Northern Ireland over past few years (almost 100 human cases since 2002)


Brucellosis – Human Infection

  1. Describe the human infection
  2. What are the clinical features?
  3. What are the complications?
  4. When does recovery normally take place?
  5. What is the treatment?
    1. Specifically, what is needed, and why?
  6. How is diagnosis made?
  7. How can it be prevented?

  1. commonly subclinical, incubation period of 2-6 weeks
  2. Fever & sweats- A rising and falling (undulant) fever, Enlarged lymph nodes and spleen, hepatitis
  3. osteomyelitis, and cholecystitis, endocarditis and meningitis are occasionally seen.
  4. The patient generally recovers after a few weeks or months - but chronic infection (>1 year), Fever depression is common feature
  5. tetracycline & co-trimoxazole. 

    1. Because of the intracellular location of the bacteria, prolonged courses of treatment (3 months) are needed. 

  6. Serology
  7. Pasteurisation


Vector-bourne infectiosn and Zoonoses

What are the key conditions, and what are the causal agents?

see picture



35 year old man presents with acute jaundice, and on investigation is found to have acute renal failure. He was recently in a canoe on the river Lagan.

What microbiological investigations? 


In a canoe

Serology - Hep A, B, C, CMV Serology

(do all of these if unaware of the canoe)

Renal and hepatic Involvement evivdent