Veterinary Parasitology Arthropod...

Veterinary Parasitology Arthropod Parasites

Melanie Buote DVM, DACVP, PhD Candidate Office: 3319 North Annex, Office phone #(902) 620-5106

Cell phone #(902) 628-5915 [email protected]

mailto:[email protected]

A little about me…

BSc, Hon Marine Bio

DVM Anatomic Pathology Residency

Diagnostic Pathologist

PhD

Met Husband

Got Married

Had Babies

Bitter Crab Disease

Bitter Crab Disease Hematodinium sp. infection:

A dinoflagellate (protozoan) parasite of decapod crustacean (arthropod) hemolymph

Outline

I. Protozoan parasites transmitted by arthropods (1 lecture)

1. Hemoflagellates • Trypanosomes and Leishmania

2. Piroplasms • Babesia and Cytauxzoon

3. Malarias • Plasmodium and Leucocytozoon

II. Arthropods (6 lectures) 1. Arachnids (3 lectures)

• Ticks and mites

2. Insects (3 lectures) • Fleas, lice, flies, and myiasis

3. Crustaceans (0 lectures) • Sea lice

Protozoan parasites transmitted by arthropods

1. Mechanical Vector • Carried by mouthparts/body • e.g. Horse flies (Tabanus)

transmit Equine Infectious Anemia on their mouthparts

2. Biological Vector • Parasite undergoes

development within arthropod vector

• Arthropod can be an intermediate host or the definitive host

• e.g. Plasmodium undergo sexual reproduction in the Anopholene mosquito (definitive host)


Piroplasms Babesia

Cytauxzoon

Hemoflagellates Trypanosoma

Leishmania

Malarias Plasmodium

Leucocytozoon


I. Hemoflagellates • Genera of veterinary importance:

1. Trypanosoma 2. Leishmania

• Morphology

• Elongate with a single flagellum or • Rounded with a non-protruding flagellum • All possess a kinetoplast

• Sausage or disc-shaped • Found at base of flagellum • Contains mitochondrial DNA

Hemoflagellate Life Cycles

Stage in

arthropod

intestine

Stage in

vertebrate

blood and/or

tissues

Chagas Disease – Zoonotic disease caused by Trypanosoma cruzi

I. Hemoflagellates 1. Trypanosomes

Section Salivaria Section Stercoraria*

Development in front portion of digestive tract of the arthropod

Development in hind portion of digestive tract of the arthropod

Transmission to vertebrate host via saliva

Transmission to vertebrate host via feces

African Trypanosomiasis -Trypanosoma congolense -Trypanosoma vivax -Trypanosoma brucei brucei

American Trypanosomiasis -Trypanosoma cruzi

*Stercorary = dung repository

I. Hemoflagellates, 1. Trypanosomes i. African Trypanosomiasis

• Major species – Trypanosoma congolense

• Cattle, sheep, goats, dogs, pigs, camels, horses, most wild animals

– Trypanosoma vivax • Cattle, sheep, goats, camels, horses, various wild animals

– Trypanosoma brucei brucei • All domestic and various wild animals • Most severe in dogs, horses, cats

– Trypanosoma simiae • Domestic and wild pigs, camels

• Transmission:

– Tsetse fly (Glossina spp.) (FYI: T. vivax can also be transmitted by biting flies in non-tsetse

areas = mechanical transmission)

I. Hemoflagellates, 1. Trypanosomes i. African Trypanosomiasis

• Bovine trypanosomiasis (Nagana)

– Sudden death in cattle (T. vivax) • Due to secondary infections (i.e., Salmonellosis)

– Chronic disease in cattle: • Anemia, cachexia, chronic ill health, abortion, reduced productivity • → ~3 million cattle deaths/year • Loss in cattle & crop production

• Nagana – many domestic species are susceptible – Cattle, equidae, small ruminants, camels, and dogs – Horses, dogs - Incoordination and spinal paralysis – Dogs - Anterior uveitis (perivascular infections)

• Animals can also host human pathogen parasites

– Domestic and wild animals = parasite reservoirs – T. brucei rhodesiense > T. b. gambiense

I. Hemoflagellates, 1. Trypanosomes ii. American Trypanosomiasis

Chagas Disease • Dogs and Humans (zoonotic) • Animal reservoirs

– Skunks, cats, pigs, raccoons, opossums, armadillos

• Cause: Trypanosoma cruzi

• Transmission:

– Triatomine bug (“Kissing bug”) – Blood transfusions

• Distribution

– Endemic in South and Central America – Low prevalence in USA (sporadic cases)

• Southern US States + Virginia/Maryland

– Potential for expansion of distribution • Where there are Triatomine bugs


Two forms of Chagas Disease in dogs: 1. Acute disease (usually young dogs <2 years old)

– Lymphadenopathy, pale mucus membranes, lethargy, hepatosplenomegaly, myocarditis, and tachyarrhythmia

2. Chronic disease – Congestive heart failure

• Heart becomes enlarged and flabby

– After extended asymptomatic period

Pathogenesis: • Multiplying amastigotes → host cell destruction → local

inflammatory response → ↑ host cell degeneration and necrosis → more inflammation…

• Preference for cardiac and skeletal muscle cells


Morphology • Trypomastigote

– Slender, 16 - 20 um long with a pointed posterior end – Found in circulating blood of the vertebrate host – Kinetoplast is near the posterior end – Flagellum is long & anterior – Narrow undulating membrane

• Amastigote

– Spheroid, 1.5 - 4.0 um, lack flagella – Develop in clusters – Found in muscle and other tissues of vertebrate host

• Epimastigote

– Kinetoplast located between the nucleus and the anterior end near the flagellum

– Found in the posterior portion of a triatomine bug’s gut

Helpful hints for remembering terms: Trypano = borer or screw-like, A = not, Mastigote = flagellate

I. Hemoflagellates, 1. Trypanosomes ii. American Trypanosomiasis (Chagas Disease)

I. Hemoflagellates, 1. Trypanosomes ii. American Trypanosomiasis(Chagas Disease)

Diagnosis • Acute infections

– Detection of trypomastigotes in blood smear or lymph

– Within 5 weeks of infection

• Chronic infections: – Culture, Serology (IFA) – Xenodiagnosis

• Naive triatomine bugs feed on host

• Look for parasites in bug’s gut

– Necropsy with histology • Clusters of amastigotes in

skeletal and cardiac muscles

I. Hemoflagellates, 1. Trypanosomes ii. American Trypanosomiasis (Chagas Disease)

Treatment & Control • Does not respond well to treatment

– Only extracellular parasites (trypomastigotes) killed – Intracellular stages (amastigotes) unaffected by treatment →

disease recrudescence

• Symptomatic treatment – Medical management of CHF

Prevention • Insecticides

– Limit & control exposure to arthropod vectors

• Avoid contact with reservoir animals – Skunks, raccoons, opossums, armadillos…

• Avoid sleeping in a mud, thatch or adobe house. – Types of residences more likely to harbor triatomine bugs


Piroplasms Babesia

Cytauxzoon


Leishmania

Malarias Plasmodium

Leucocytozoon



Leishmania

I. Hemoflagellates

1. Trypanosomes

i. African Trypanosomiasis

ii. American Trypanosomiasis (Chagas Disease)

2. Leishmania

I. Hemoflagellates 2. Leishmania (Leishmaniasis) Hosts • Dogs and Humans (zoonotic) • Rodents, wild mammals, rare in cats • Horses, mules, donkeys Cause: • Leishmania donovani species complex Transmission: • Female sandflies

– Phlebotomus sandflies (Eastern Hemisphere) – Lutzomyia sandflies (Western Hemisphere )

• Blood transfusion • +/- vertical and horizontal transmission

I. Hemoflagellates 2. Leishmania Distribution: • Endemic in the tropics: Mediterranean, Middle East, Asia, Central +

South America • Sporadic reports in North America: English & American Foxhounds

in USA, Southern Ontario, & Nova Scotia

I. Hemoflagellates 2. Leishmania Clinical forms of leishmaniasis 1. Cutaneous leishmaniasis

– Non-specific skin lesions – Alopecic or nodular forms (few vs. many

organisms in lesions), – Often affects the head/face and limbs,

+/- chronic ulcers, +/- nail deformites, secondary infections common

– +/- systemic infection

2. Visceral leishmaniasis – Non-specific systemic signs – Poor body condition, rough hair coat,

chronic wasting, recurrent oculonasal discharge, recurrent diarrhea, mildly enlarged lymph nodes, hepatosplenomegaly with granulomas

I. Hemoflagellates 2. Leishmania Pathogenesis

• Leishmania organisms are engulfed by macrophages → multiply rapidly (binary fission) and destroy the macrophage → engulfed by more macrophages → formation of granulomas in skin and organs

• Destruction of cells (i.e., macrophages) from the reticuloendothelial system → ↑ susceptibility to secondary pathogens

I. Hemoflagellates 2. Leishmania

I. Hemoflagellates 2. Leishmania Morphology

• Amastigote – Spheroid, lack flagella, 2.5 - 5.0 um

– Found in the vertebrate hosts tissue

– Often found within macrophages

– Kinetoplast is oriented perpendicular to nucleus (lollipop)

• Promastigote – found in the gut of the sandfly vector

– forward extending flagellum

– kinetoplast is located near the anterior end of the body

Helpful hints for remembering terms: A = not; Pro = before, earlier, or in favor of; Mastigote = flagellate


• Diagnosis – Fine needle aspirates (FNAs) of enlarged

organs and/or granulomas (liver, spleen, lymph nodes, skin nodules) or bone marrow aspirates • Amastigotes within macrophages or free

(ruptured host cells) – BUT beware of false negative FNAs!

– Biopsy with histopathology

– Detect antibodies to parasite in serum – Immunofluorescent Antibody test (IFA)

– Enzyme-Linked Immunosorbent Assay (ELISA)

– Q-PCR for detection of parasite


• Treatment and Control – Symptomatic medical treatment to reduce the clinical

signs of disease (not curative) • Meglumine Antimoniate with Allopurinol, Aminosidine &

Amphotericin B • All drugs require multiple dose regimens • Depend on the patient's condition & owner cooperation

– Relapse is common • Weeks, months or years later

– Vector control is essential • Use of insecticide collars, shampoos or sprays • Especially in patients under treatment • Residual insecticide spraying of houses & animal shelters

may help


Piroplasms Babesia

Cytauxzoon


Leishmania

Malarias Plasmodium

Leucocytozoon



i. African Trypanosomiasis and Nagana ii. American Trypanosomiasis (Chagas Disease)

2. Leishmania i. Leishmaniasis

II. Piroplasms 1. Babesia 2. Cytauxzoon 3. Theileria

II. Piroplasms

• Piriform (pear-shaped) intracellular apicomplexan parasites

• Parasites of blood cells in vertebrates

• Transmitted by ixodid (hard) tick vectors

II. Piroplasms

Morphology 1. Babesia spp.

– Merozoites are found in the erythrocytes of the vertebrate host

– Piriform to amoeboid – 3 - 5 µm long and 2 - 4 µm in diameter

• Size is species dependent

– Blue cytoplasm with red chromatin mass (Wright-Geimsa)

2. Cytauxzoon felis – Signet-ring like merozoites found in

erythrocytes – 1 - 1.2 µm in diameter – Merozoites may be found within

monocytes/macrophages (histiocytes) in spleen, lymph nodes, lungs, liver and kidneys

Piroplasmosis – Human Babesiosis

1. Babesia spp. – Schizogony in

erythrocytes

2. Cytauxzoon sp. – Schizogony in

erythrocytes and histiocytes (macrophages)

3. Theileria spp. – Schizogony in

lymphocytes (+/- macrophages)

Schizogony = Merogony

(asexual reproduction via fission giving rise to merozoites)

II. Piroplasms

Pathogenesis 1. Babesia spp.

– Destruction of parasitized erythrocytes → hemolytic anemia → lethargy, inappetance, jaundice, dehydration, dark urine

– Clogging of capillaries in various organs by parasitized cells & free parasites → anoxia, accumulation of toxic metabolites, hemorrhaging & organ failure

– Most characteristic feature of B. bovis infections is a cerebral flush (diffuse reddening of gray matter of brain due to capillary congestion)

2. Cytauxzoon sp. – Destruction of parasitized erythrocytes → hemolytic anemia → lethargy,

inappetance, jaundice, dehydration, dark urine – Infected histiocytes (macrophages) can clog venules in organs and

infiltrate tissues (liver, spleen, lungs, lymph nodes, bone marrow) → hepatosplenomegaly, lymphadenomegaly

– +/- ↑ liver enzymes & prolonged clotting times – Pancytopenia can be seen (↓RBCs, ↓WBCs, ↓platelets)

II. Piroplasms Diagnosis 1. Babesia spp.

– History, clinical signs, serology – Observation of merozoites within erythrocytes on

stained blood smears – Collected blood from ear, tip of the tail, or toe nail as

parasites are more common & numerous in capillary blood

2. Cytauxzoon felis – History & clinical signs – Observation of merozoites within erythrocytes on

stained blood smears • Intraerythrocytic parasites need to be differentiated from

Babesia felis and Mycoplasma haemofelis

– Observation of merozoites in histiocytes (macrophages) in tissue impression smear (cytology) or histology (biopsies or necropsies) • Intrahistiocytic stages = diagnostic

II. Piroplasms

Treatment & Control 1. Babesia

– Diaminazene I.M. or phenamide S.C.

2. Cytauxzoon – Rapidly fatal disease – No treatment has proven effective

Prevention • Tick control • Ticks are rarely seen on cats (grooming behavior)

Piroplasmosis – Ixodid Tick Vectors (FYI) Disease Causative agent Ixodid Tick Vector

Bovine Babesiosis (“Red Water Fever”)

Babesia bigemina Rhipicephalus (Boophilus) annulatus (eradicated)

Bovine Babesiosis (“Red Water Fever”)

Babesia bovis Babesia divergens Babesia argentina

Rhipicephalus (Boophilus) microplus

Bovine Theleiriosis (“East Coast Fever”)

Theileria parva Rhipicephalus appendiculatus

Canine Babesiosis Babesia gibsonii Rhipicephalus sanguinensis (brown dog tick)

Feline Cytauxzoonosis Cytauxzoon felis (bobcat wildlife reservoir)

Dermacentor variablis (presumed)

Equine Babesiosis Babesia caballi Theileria (Babesia) equi

Genera: Dermacentor, Hyalomma, and Rhipicephalus

Human Babesiosis (Zoonosis)

Babesia microti (parasite of voles and mice)

Ixodes scapularis


Piroplasms Babesia

Cytauxzoon


Leishmania

Malarias Plasmodium

Leucocytozoon



i. African Trypanosomiasis and Nagana ii. American Trypanosomiasis (Chagas Disease)

2. Leishmania i. Leishmaniasis

II. Piroplasms 1. Babesia 2. Cytauxzoon 3. Theileria

III. Malarias 1. Plasmodium 2. Leukocytozoon 3. Haemoproteus

III. Malarias 1. Plasmodium spp.

– Avian Malaria and Human Malaria

– Transmitted by mosquitoes

2. Leucocytozoon spp. – Parasites of domestic & wild birds

– Over 60 species known to infect birds

– Transmitted by the black fly, Simlulium spp.

3. Haemoproteus spp. – Birds and reptiles

– Usually an incidental finding

(i.e., non-pathogenic)

– Transmitted by louse flies & biting midges

III. Malarias

1. Plasmodium spp. • Humans & non-human primates, rodents, birds & reptiles

– Human Malaria – Avian Malaria

• Transmission – Mammals - anopheline mosquito (Anopheles spp.) – Birds - culicine mosquito (Culex spp.)

• Human malaria – Between 100-300 million people are infected/year – ~1 million people die from malaria each year – 90% of deaths due to Plasmodium falciparum – P. knowlesi in macaques = zoonotic

FYI: • Female mosquitoes use two volatile cues to select and navigate toward hosts:

1. Exhaled CO2 2. Skin odorants

• Female mosquitoes detect plumes of exhaled CO2 using a class of olfactory receptor neurons (ORNs) designated cpA.

• CpA neurons are housed in capitate peg (cp) sensilla on the maxillary palps and express the CO2 receptor, comprising three conserved members of the Gustatory receptor gene family

Avian Malaria

• Numerous species of genus Plasmodium – Plasmodium relictum

• Transmission – To birds by culicine mosquito (i.e., Culex spp.)

• Clinical signs – Anemia, lethargy, hepatomegaly, and hepatitis – Can be fatal in non-adapted species

• Penguins (animals in captivity) • Hawaiian forest birds

– Hawaiian crows, honeycreepers (apapane < i’iwi)

III. Malarias

2. Leucocytozoon spp. – Transmitted by the black fly

• Simulium spp.

– Parasites of birds • Domestic & wild

– Over 60 species • L. simondi

– Infects ducks & geese

(Canadian geese)

• L. caulleryi – Infects chickens

• L. smithi – Infects turkeys

III. Malarias 2. Leucocytozoon

1. Black fly transmits sporozoites to vertebrate host → Sporozoites disseminate and infect a variety of cell types and undergo shizogony (esp. in liver) → cell lysis → merozoites released

2. Merozoites infect RBCs, WBCs, and endothelial cells → gametocytes

• Merozoites in RBCs → ROUND gametocytes

• Merozoites in endothelial cells → megaloschizonts → merozoites → invade WBCs → ELONGATE gametocytes

3. Gametocytes ingested by black fly → sporogony in gut & salivary glands

III. Malarias, 2. Leucocytozoon Pathogenesis • Destruction (lysis) of infected host cells • Ruptured schizonts may induce

granulomatous reactions in the surrounding tissues

• Results in anemia, leukocytosis, splenomegaly, & hepatomegaly

• Megaloschizonts appear as grey-white nodules – Found in the heart, liver, lung or spleen.

• Megaloszhizonts in endothelial cells → occlusion of blood vessels → ischemic necrosis and associated inflammation in the heart, brain, spleen, and liver

• Livers are variably enlarged and pale, may contain nodules (megaloschizonts +/- granulomas), and often contain areas of hemorrhage

III. Malarias 2. Leucocytozoon Clinical signs • Majority of birds affected with leukocytozoonosis

exhibit no signs. • Young birds (most susceptible)

– Acute onset of anorexia, listlessness, laboured breathing, anemia (pallor), diarrhea (with green droppings)

– Susceptibility to secondary infections is increased. – Significant death loss within 24 hours of clinical signs – Typically signs appear 10 - 19 days post exposure

• Older birds – Chronic infections with low mortality, but can

become listless & thin – ↓ egg production, egg weight & hatchability – Recovered birds harbour the parasite in their blood

for over a year & often for life

III. Malarias 2. Leucocytozoon Diagnosis • Blood smears

– Microscopic observation of gametocytes in stained thin blood smears

– Round & elongate gametocytes!

• Necropsy with histology – Identification of schizonts and

megaloschizonts in tissue sections

• New PCR test (research only)

III. Malarias, 2. Leucocytozoon

Treatment & Control • Preventive medication is the norm • Sulfadimethoxine & pyrimethamine combinations • Clopidol has been approved by the FDA for

control of infections in turkeys

Prevention • Control black fly vector • Keep domestic birds separated from wild birds (wildife reservoirs)

Simulium black fly


Piroplasms Babesia

Cytauxzoon


Leishmania

Malarias Plasmodium

Leucocytozoon


Piroplasms Babesia

Cytauxzoon


Leishmania

Malarias Plasmodium

Leucocytozoon

Trypomastigotes in blood

Amastigotes in macrophages

Merozoites in RBCs

Merozoites in RBCs (& mø)

Merozoites in RBCs

Merozoites in RBCs, round & elongate gametocytes in blood


1. Hemoflagellates 1. Trypanosomes

i. African Trypanosomiasis and Nagana (Tsetse fly) ii. American Trypanosomiasis (Chagas Disease; Triatomine “kissing” bug)

2. Leishmania i. Leishmaniasis (Sandflies)

2. Piroplasms 1. Babesia (Ixodid ticks) 2. Cytauxzoon (Ixodid ticks)

3. Malarias 1. Plasmodium (Mosquitoes) 2. Leukocytozoon (Black flies)


Protozoan Vector Host Disease

Trypanosoma congolense, T. vivax, T. brucei brucei

Tse tse fly (Glossina sp.)

African cattle (etc.)

Bovine trypanosomiasis (Nagana)

Trypanosoma cruzi Triatomine (kissing) bug (Triatoma sp.)

Dogs Chagas Disease

Leishmania donovani complex

Phlebotomus sandfly Lutzomyia sandfly

Dogs Leishmaniasis

Babesia bovis Ixodid tick (Rhipicephalus appendiculatus)

Cattle Bovine babesiosis

Babesia gibsonii Ixodid tick (Rhipicephalus sanguinensis)

Dogs Canine babesiosis

Cytauxzoon felis Ixodid tick (Dermacentor variabilis)

Cats (bobcats) Cytauxzoonosis

Plasmodium relictum Culicine mosquito (Culex spp.)

Birds Avian malaria

Leucocytozoon simondi Simulium black fly (Simulium spp.)

Ducks & geese & Chickens & Turkeys

Leucocytozoonosis

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