Arthropod-Vector Borne Infectious Diseases in Small Animals

Question 1

What are vector-borne diseases caused by?

Answer 1

Parasites, bacteria or viruses transmitted by the bite of haematogenous arthropods

Question 2

What is the purpose of the Pet Travel Scheme (PETS)?

Answer 2

To protect individual pets but also UK disease status and requires rabies and tapeworm treatment

Question 3

What changes have recently been made to the PETS?

Answer 3

On 1st Jan 2012 the requirement for compulsory treatment of companion animals for ticks before their entry into the UK was withdrawn

Question 4

What tick borne diseases may be imported in dogs travelling in from the EU?

Answer 4

Babesia canis canis
Babesia gibsoni
Ehrlichia canis

Question 5

What tick borne diseases are already endemic in the UK?

Answer 5

Borrelia burgdorferi

Anaplasma phagocytophilum

Question 6

Which ticks are already endemic in the UK?

Answer 6

Ixodes ricinus

Dermacentor reticulatus

Question 7

Which tick is brought into the UK on animals?

Answer 7

Rhipicephalus sanguineus - not endemic in UK and requires >18C for life cycle, vector for Mediterranean spotted fever

Question 8

What is babesiosis caused by?

Answer 8

Protozoan parasite of RBCs transmitted by ticks

2 main genera are Babesia and Theileria = Piroplasms

Question 9

What are the most important agents of canine babesiosis?

Answer 9

Large babesia = B. canis canis (Europe), B. canis vogeli (Africa, Asia, USA, Europe, Australia), B. canis rossi (S. Africa)
Small babesia = B. gibsoni (Asia, Africa, USA, S. Europe)

Question 10

What differences exist between the different species of babesia?

Answer 10

Vectors and geographical distribution (changing)

Virulence, prognosis and response to treatment

Question 11

What is the pathogenesis of babesia?

Answer 11

Within ticks Babesia is transmitted trans-stadially and trans-ovarially
Sporozoites injected from tick salivary glands, enter circulation and endocytosed by RBCs
Immune-mediated component of pathology
Thrombocytopaenia common but usually not enough to cause bleeding or abnormal coagulation

Question 12

What are the clinical signs of babesiosis?

Answer 12

Those of haemolytic anaemia

Lethargy, depression, inappetence, icterus, splenomegaly, tachycardia, tachypnoea

Question 13

How is babesia diagnosed?

Answer 13

Clinical lab findings - thrombocytopaenia, Coombs +ve
Microscopic identification - low sensitivity
PCR - high sensitivity, species identification possible
Serology - indirect fluorescence Ab test/ELISA

Question 14

What is the treatment for babesiosis?

Answer 14

Antibabesial drug - Imidocarb dipropionate
Large forms = rapid clinical response
Small forms = clinical and pathological cure uncommon, clinical relapses can occur

Question 15

Which rickettsial diseases are vector borne?

Answer 15

Canine Ehrlichia and Anaplasma spp

Small obligate intracellular gram -ve bacteria

Question 16

Which species infect monocytic cells?

Answer 16

Ehrlichia canis

Ehrlichia chaffeensis which causes human form but molecular evidence has been found in canine form

Question 17

Which species infects thrombocytic cells?

Answer 17

Anaplasma platys

Question 18

Which species infects granulocytic cells?

Answer 18

Anaplasma phagocytophilum

Ehrilichia erwingii

Question 19

What is the incubation period of Ehrlichia canis?

Answer 19

1-3 weeks

Question 20

What are the acute signs of Ehrlichia canis?

Answer 20

Vasculitis and immune destruction causing thrombocytopenia and coagulopathy
Multisystemic signs
Spleen and LN enlargement
CNS/ocular sings

Question 21

What are the two outcomes of acute Ehrlichia canis?

Answer 21

Clearing of disease

Sub-clinical carriers

Question 22

What can happen to the sub-clinical carriers of Ehrlichia canis?

Answer 22

Recover or become chronically infected

Question 23

What are the signs of chronic Ehrlichia canis infection?

Answer 23

Bone marrow destruction causing a pancytopenia

Signs as for acute

Question 24

How is Ehrlichia canis diagnosed?

Answer 24

Morulae in monocytes in blood smears or macrophages from tissue aspirates
Thrombocytopaenia/pancytopaenia
IFA/ELISA

Question 25

How is Ehrlichia canis treated?

Answer 25

Tetracyclines/Chloramphenicol for 28 days

Question 26

What are the signs of A. phagocytophilum in dogs?

Answer 26

Mild/moderate thrombocytopaenia Lymphopaenia Mild anaemia Natural chronic infection hasn't been seen Impaired PMN function can predispose to secondary infections

Question 27

What are the clinical signs of Lyme disease in people?

Answer 27

Erythema migrans in 80-90% of cases | Later clinical signs involve skin, nervous/musculoskeletal systems

Question 28

What are the commonest signs of Lyme disease in dogs?

Answer 28

Lethargy, anorexia and pyrexia Inflammatory polyarthritis Lymphadenopathy Protein-losing glomerulonephropathy

Question 29

How is diagnosis of Lyme disease achieved in dogs?

Answer 29

No pathognomonic test Asymptomatic seroconversion common Microscopic/genetic detection often not possible

Question 30

What is the treatment for Lyme disease in dogs?

Answer 30

Doxycycline/amoxicillin

Question 31

What are the characteristics of Leishmania?

Answer 31

Flagellate protozoa Phlebotomus vector - sandflies Reservoir host - dogs

Question 32

What is the life-cycle of Leishmania?

Answer 32

IMAGE

Question 33

What are the key features of pathogenesis of canine leishmaniosis?

Answer 33

Macrophages are target tissues Systemic infection in haemolymphatic organs Parasite persistence can lead to chronic infection Protective immunity mediated by T cells Signs may develop months-years after infection

Question 34

How does host immune response determine clinical outcome?

Answer 34

Th2 predominant = severe non self-limiting disease with high serology, decreased cellular immunity and high parasite load Th1 predominant = clinically healthy but infected self-limiting disease with low serology, predominant cellular immunity, low parasite load

Question 35

What other factors influence variation of clinical outcome?

Answer 35

Endemic/naive situation, 2-4 years and >7 years more susceptible Breed, nutrition, concurrent disease and immunosuppression

Question 36

What are the clinical signs of leishmaniosis?

Answer 36

Weight loss, lethargy, inappetence, skin disease, lymphadenomegaly, splenomegaly, lameness, arthropathy, PU/PD, proteinuria, ocular signs, epistaxis, GI signs, hypergammaglobulinaemia, non-regenerative anaemia or mild thrombocytopaenia, azotaemia

Question 37

How is leishmaniosis diagnosed?

Answer 37

Demonstration of parasite (100% spec, 80% sens) Serology with high Ab titre highly suggestive PCR of bone marrow/LN/spleen/skin Clinicopathological findings - hyperglobulinaemia, decreased albumin:globulin ratio, thrombocytopaenia, non-regenerative anaemia, proteinuria

Question 38

What is the treatment for leishmaniosis?

Answer 38

Meglumine antimoniate + allopurinol (prolonged treatment) and needs importation as not licensed in UK

Question 39

What does Diroflaria immitis cause?

Answer 39

Heartworm | Occupy R side heart and pulmonary arteries

Question 40

What are the clinical signs of D. immitis?

Answer 40

Coughing, dyspnoea, reduced exercise tolerance, R sided heart failure

Question 41

What vector transmits D. immitis?

Answer 41

Mosquito

Question 42

What are the prophylactic treatments for D. immitis?

Answer 42

Selamectin (Stronghold) Milbemycin (Program Plus/Milbemax) Moxidectin (Advocate)

Question 43

What is the treatment for D. immitis infection?

Answer 43

Symptomatic treatment with steroids and treatment of CHF Adulticide therapy using melarsomine Microfilarial therapy using levamisole, ivermectin, milbemycin

Question 44

What is Bartonellosis?

Answer 44

Caused by small gram -ve haemotropic bacteria

Question 45

Which species of Bartonella is most common in cats?

Answer 45

Bartonella henselae most common in cats

Question 46

What is the vector for Bartonella?

Answer 46

Fleas | Ticks?

Question 47

How are zoonotic bartonella infections caused?

Answer 47

Cat scratch disease