Protozoa

How quickly do oocysts associated with neospora sporulate and become infective?

24-72 hours following passage in feces, persists for several days Puppies typically shed more oocysts compared to adult dogs

What is the caustive agent of toxoplasmosis?

Toxoplasma gondii

What are the typical clinical signs associated with Cytauxzoonosis?

- Acute onset of profound lethargy and anorexia - Elevated nictan membranes - Tachypnea/dyspnea - Icterus - Fever *these clinical signs are due to schizogony (rather than hemolysis caused by piroplasms). Schizont-distended mononuclear cells occlude small veins and capillaries, most notably in the liver, lung, spleen, and lymph nodes. The end results can be sepsis, DIC, and multiorgan failure.

What are the classic clinical signs associated with H.Americanum?

- Fever - Myositis - Severe pain and hyperesthesia - Bone lesions (can look like HO but tend to be proximal rather than distal) - Mucopurulent ocular discharge Dogs with American canine hepatozoonosis frequently maintain a fairly normal appetite; however, weight loss, cachexia, and muscle atrophy occur over time. There may be a history of polyuria and polydipsia that is due to glomerulonephritis or amyloidosis, which can occur secondary to long-standing inflammation. Nephrotic syndrome and thromboembolic complications may ensue.

Some cats with high burdens of tachyzoites or underlying immunodeficiency (such as FIV) will develop clinical disease associated w/ toxoplasmosis. What organ systems does it typically affect?

- Hepatic - Pulmonary - CNS - Pancreatic tissues

What does chronic toxoplasmosis typically manifest as in cats?

- Uveitis - Chorioretinitis - Cutaneous lesions - fever - muscle hyperesthesia - myocarditis with arrythmias - Weight loss - Anorexia - seizures - icterus - diarrhea - respiratory distress - pancreatitis

What is the geographic distribution of toxoplasmosis? What is the one exception to this rule?

- Worldwide distribution - Cats are the definitive host and the only species known to complete the sexual phase of T.gondii culminating in the passage of infective oocyts in the feces. Therefore, without cats, you couldn't have toxo!

How quickly can toxoplasmosis oocysts become infectious once in the environment and exposed to oxygen & appropriate temperature/humidity? This process is referred to as sporulation!

1-5 days

What are treatment options for leishmaniosis?

1. Allopurinol 2. Meglumine antimoniate and sodium stibogluconate 3. Amphotericin B 4. Miltefosine Combination of allopurinol & meglumine* is the treatment of choice. Treat until clinical signs have resolved and quantitative serology becomes negative.

Describe the lifecycle of hepatozoonosis.

1. As it feeds on an infected dog, the nymphal tick ingests circulating leukocytes that contain gamonts. 2. Within the tick's gut, the gamonts are freed from the cells and undergo further development before fertilization occurs. 3. The resulting zygote divides through sporogony and develops into an oocyst within the hemocoel of the tick. 4. Oocysts mature while the tick molts to the adult stage. In the case of H. americanum, the larval stage of the tick can also become infected, resulting in a nymph that contains viable oocysts capable of transmitting the disease.37 Each mature oocyst contains hundreds of sporocysts, with each sporocyst containing 10 to 26 infective sporozoites. 5. Preferentially the infected cells travel to skeletal muscle, where each organism develops within its host cell.

Describe the process of enteroepithelial replication for toxoplasmosis gondii.

1. Cats are not typically coprophagic so will ingest the meat that has bradyzoite. 2. Bradyzoite transforms into a merozoites, which replicates in the epithelial cells of the intestinal tract. Then it will turn into microgamete and macrogamate > lead to zygote. 3. Zygote released into GI tract as an unsporulated oocyst. 4. Unsporulated oocyst are shed for 3-21 days in the feces

What are diagnostic modalities available to detect H.Caninum?

1. Cytology of whole blood can be performed to search fro gamonts within the cytoplasm of neutrophils or monocytes 2. PCR is available through Auburn University. Although highly sensitive and specific, false negatives can occur early in the course of infection or in dogs with chronic disease where the numbers of circulating gamonts are extremely low or absent. 2. Histopathology of muscle biopsies - can be difficult because you can miss the lesion. For H. americanum infections, muscle biopsy has long been considered the most reliable method for diagnosis. Small pieces of muscle (approximately 2 cm × 2 cm) are obtained from the biceps femoris or semitendinosus muscles under general anesthesi

What diagnostic modalities are available for leishmaniosis?

1. Identification of Leishmania spp. amastigotes in lesions with cytology is diagnostic for leishmaniosis 2. IFA is available in Europe (will be negative early in disease, may cross react w/ vaccine) but has a high sensitivity (90-100%) and decent specificity (80-100%).

From a zoonotic perspective, who are the most at risk for toxoplasmosis infections?

1. Immunocompromised people (AIDS patients unfortunately get toxoplasmosis) 2. Pregnant people can acquire transplantal infection & lead to fetal damage

What are the modes of transmission for intermediate hosts?

1. Ingestion of any of the three lifestages (sporozoite in oocysts, tachyzoites, or bradyzoites in infected meat) 2. Transplacental

Describe the lifecycle of cytauxzoon felis.

1. Piroplasms are found in host RBCs and ingested by ticks when they feed on these infected hosts. 2. The organism undergoes sexual replication in the tick and forms sporozoites. 3. The tick innoculates sporozoites in the new host when they feed on them. 4. Approximately 2 weeks after inoculation, schizogony occurs, whereby mononuclear cells become distended with parasites. 5. These cells rupture and merezoites are released > taken up by RBCs as piroplasms.

Describe the life cycle of leishmaniasis, focusing on which stages feature the promastigote and mastigote.

1. The promastigote lives in the gut of the sandfly vector and is an elongated, flagellated form. 2. Promastigotes are inoculated into tissues when the sandfly feeds, where they are phagocytized by macrophages in the dermis and transform into intracellu- lar, nonmotile, ovoid, or round amastigotes. Eventually the macrophage ruptures and releases the amastigotes. 3. . Released amastigotes then infect other macrophages that have been attracted to the site of infection. If the infected host fails to control the infection, amastigotes disseminate via regional lymphatics and the blood to infect the entire reticuloendothelial system.

What are diagnostic modalities available for diagnosis of toxoplasmosis?

1. Using cytologic examination, T. gondii bradyzoites or tachyzoites can be detected in tissues, effusions, bronchoalveolar lavage fluids, aqueous humor, or CSF. 2. Paired IgM and IgG titers 3. Fecal Float? No dice man. It has a poor negative predictive value since oocyst shedding is so short and occurs way before clinical signs start.

What is the vector for Chagas' disease?

A bite from, or ingestion of, reduviid (kissing bug) vectors, primarily Triatoma species.

What is the tick vector for cytauxzoon felis?

Amblyomma Americanum

Explain why it is unlikely a cat with toxoplasmosis will shed oocysts throughout its lifetime.

Although T. gondii infection is common among cats, the oocyst shedding period is generally less than 21 days. Thus, detection of T. gondii oocysts in feline feces is uncommon.

What are the intermediate hosts of toxoplasmosis? (i.e. who can it infect and cause disease in?)

Any warm blooded vertebrate

What are the principle wildlife reservoirs in Southern States (TX, Lousianna, etc.)?

Armadillos, opossums, and racccoons

What is the treatment of choice for Cytauxzoon felis?

Atovaquone & Azithromycin

What is the reservoir species for cytauxzoon felis?

Bobcats

What is the caustive agent of visceral leishmaniosis? What about the cutaneous form (American tegumentary leishmaniosis)?

Canine and feline visceral leishmaniosis is caused by Leishmania infantum Other species such as L. braziliensis cause localized cutaneous lesions in South America (American tegumentary leishmaniosis).

What is the geographic distribution of Chagas' disease?

Central and South America; to a lesser extent southern United States (especially south- eastern Texas) **it's really an issue of Texas tbh

What antibiotic is used to treat neosporosis?

Clindamycin

What is the treatment for toxoplasmosis?

Clindamycin or a trimethoprim-sulfonamide combination has been prescribed most frequently for the specific treatment of clinical toxoplasmosis. Treat for a week to see if there is positive improvement (switch to the other drug if not) and continue for 4 weeks total.

What is the MOA of decoquinate?

Decoquinate, a livestock anticoccidial agent, apparently breaks the asexual recycling of infection by arresting development of the merozoites after their release from meronts.

What diagnostic modalities are available to confirm the diagnosis of neosporosis?

Diagnosis most often relies on serology or detection of protozoal organisms in body fluids, aspirates, or tissues using light microscopy and/or PCR assays. With that said, detection of organism is very difficult so serology is what we go with.

What is the definitive host of neospora?

Dogs + wild canids (coyotes, wolves, etc.) are the definitive hosts and are the only species known to complete the sexual phase of N. caninum replication with passage of oocysts in the feces. Clinical illness can occur in cattle, sheep, or water buffalo but these are intermediate hosts.

What is the mode of transmission for neospora?

Dogs can be infected transplacentally or transmammary route. Postnatally, dogs may be infected after they ingest infected tissues of intermediate hosts or bovine fetal membranes

What's the thought process behind dogs who clear leishmaniosis versus those who don't?

Dogs with excellent CMI responses are likely to eliminate the infection. The dogs who mount weak CMI despite a marked, humoral (IgG) immune response develop clinical disease.

What animals are most commonly affected by hepatozoonosis? These are also the intermediate hosts for the protozoa.

Domestic dogs

What specific clinical signs are seen in the eyes with Cytauxzoon felis?

Elevated nictitating membranes

What is the most common CBC abnormality in H.Americanum?

Extreme leukocytosis (WBC 20K - 200K), characterized by mature neutrophilia +/- bands

T/F: Dogs with H.Canis typically display moderate to severe clinical illness.

False - dogs with H.Canis typically have mild clinical signs that are exacerbated by immunosuppression. Dogs with H.Americanum however develop moderate to severe clinical illness.

T/F: More than 52% of cats with positive seroprevalence for toxoplasmosis will develop clinical signs.

False, less than a percent of cats in the US will develop clinical signs. In general, the enteroepithelial cycle in the cat rarely leads to clinical signs.

T/F: Dogs with H.Americanum typically are thrombocytopenic.

False, run a 4DX on this dog because it's likely he has another tick coinfection like erlichiosis.

T/F: Dogs with H. Americanum often have markedly elevated CK.

False. Surprisingly, the activity of serum CK is consistently within the normal range even though H. americanum infection causes severe myositis.

T/F: Hepatozoonosis is acquired by getting bitten by an infected tick.

False. Unlike most tick-borne diseases, hepatozoonosis is not transmitted through the bite of an infected tick but rather by ingestion of an infected tick.

What sort of peak does leishmaniosis appear like on serum protein elecrophoresis?

Frequently polyclonal, rarely monoclonal

What is the geographic distribution of hepatozoonosis?

H.Americanum - southeastern & southcentral US (Gulf Coast of Texas, Louisiana, Oklahoma, Alabama, Georgia, Florida, and Tennessee). H.Canis - really an issue in other countries such as Asia, Africa, southern Europe, etc.

What is the primary vector for hepatozoon?

H.Canis - Rhipicephalus Sanguineus (brown dog tick) H.Americanum - Amblyomma maculatum (Gulf coast tick)

Who will have piroplasms - healthy cats or sick cats that are infected with cytauxzoon?

Healthy cats - piroplasms Sick cats - piroplasms & shizonts

What are the causative agents of hepatozoonosis?

Hepatozoon canis and hepatozoon americanum

What is the general thought process behind serology with toxoplasmosis testing?

IgM is formed approximately 2-4 weeks after infection, and these titers wane and become negative after 4 months. IgG become elevated 3-4 weeks following infection & persistently elevated for life.

What are the classic clinical signs associated with Chagas disease?

In North America, disease in dogs usually manifests as cardiac disease typified by arrhythmias or myocarditis (acute or chronic), and, rarely, neurologic disease.

What is the likelihood of finding a gamont within a white blood cell in a dog infected with H.Americanum? How can you improve your yield?

In dogs with H. americanum infection, gamonts are rarely found within monocytes or neutrophils on peripheral blood smears. When present, infected cells rarely exceed 0.1% of the circulating leukocytes; several thousand cells may have to be examined before an infected cell is found. In other words, it's very rare! By looking at the buffy coat.

What clinical signs do dogs with toxoplasmosis typically develop?

In dogs, respiratory, gastrointestinal, or neuromuscular infection with associated signs of fever, vomiting, diarrhea, respiratory distress, ataxia, seizures, and icterus occurs most commonly with generalized toxoplasmosis. Dogs with myositis present with weakness, stiff gait, or muscle atrophy. Rapid progression to tetraparesis and paralysis with lower motor neuron dysfunction can occur (probably some of these dogs had neospora).

What is the reservoir host for leishmaniosis?

Infected dogs

What is the following protozoal species?

Intracellular (within neutrophils) neospora tachyzoites

What is the clinical outcome of becoming infected with leishmaniosis?

It's incredibly variable. Some dogs are subclinically infected and only develop illness in the face of immunosuppression; a small percentage of dogs develop severe illness. Some dogs completely clear the infection.

What does treatment look like for H.Americanum?

Lifelong. Treatment of clinical signs can be abated with TMS, clindamycin, and pyrimethamine for 14 days. But they need to receive the anti-cocciodal medication decoquinate for life or else, relapse.

What is the causative agent of neosporosis?

Neospora caninum

Why is an entire litter of puppies often infected by neospora in a subclinical bitch?

Pregnancy reactivates dormant bradyzoites in the tissues & leads to tachyzoites that can either cause abortion or infection via the transplacental route.

What is the major mode of transmission of leishmaniosis?

Phlebotomus (old world) and Lutzomyia (new world) sandflies

What is the geographic distribution of leishmaniosis?

Primarily southern Europe and the Middle East, central and South America; also some parts of the United States. Travel-related disease can occur in non-endemic regions worldwide.

What does serology detect for neospora? Should you submit it on serum or CSF?

Serologic assays are available commercially that detect antibody to N. caninum in serum and/or in CSF. Titers are often higher in serum than in the CSF of affected dogs.

What is the geographic distribution of cytauxzoon felis?

Southeast, southcentral & mid-atlantic states

A pregnant client asks you to test her healthy cat for toxoplasmosis. You perform routine diagnostics as well as toxoplasmosis titers. The results of the titers are: IgM - Negative IgG - Positive, 1:6,400 What does this mean? Is the cat an immediate risk factor for the woman?

T. gondii IgG antibody titers can be detected for at least 6 years after infection in experimentally inoculated cats; because the organism probably persists in tissues for life, IgG antibodies probably do as well. Single, high IgG titers do not necessarily suggest recent or active T. gondii infection; healthy cats can have titers that exceed 1:10,000 as long as 6 years after experimental induction of toxoplasmosis.

Describe the lifecycle of T.Cruzi.

T.Cruzi has three morphologic forms. 1. The form that circulates freely in the host's peripheral blood is the trypomastigote. This form is 15 to 20 μm long, with a flattened spindle-shaped body and a centrally placed vesicular nucleus. A single flagellum originates near a large, subterminal kineto- plast (situated posterior to the nucleus) and passes along the body to project anteriorly 2. Amastigote, which lives intracellularly. Approximately 1.5 to 4.0 μm in diameter, is roughly spheroid, and contains both a nucleus and a rod-like kinetoplast. 3. The third morphologic form, the epimastigote, is found in the arthropod vector, a reduviid or "kissing bug" (subfamily Triatomae). Epimastigotes are flagellated and spindle shaped with the kinetoplast situated anterior to the nucleus. When a vector is involved in transmission, infection occurs when trypomastigotes are deposited in the triatomine's feces at the insect bite site. Kissing bugs frequently defecate after feeding so this is a common mode of infection.

Describe the pathway T.Gondii takes in most mammalian cells (asexual reproduction essentially).

T.gondii sporozoites are usually acquired by oro-fecal exposure to eggs. They can penetrate most mammalian cells and replicate asexually until the cell is destroyed. If an appropriate immune response occurs, replication of tachyzoites is attenuated and slowly dividing bradyzoites develop that persist within cysts in extraintestinal tissues. These tissue cysts form readily in the central nervous system (CNS), muscles, and visceral organs. Live bradyzoites may persist in tissue cysts for the life of the host.

What life stage is this toxoplasma gondii organism demonstrating?

These are sporulated oocyts of toxoplasmosis gondii

This was found in the peripheral blood smear of an outdoor cat with icterus on presentation. What's your diagnosis?

These are cytauxoon felis piroplasms within a RBC

This was found in the peripheral blood smear of an outdoor cat with icterus on presentation. What's your diagnosis?

These are cytauxoon felis schizonts within a mononuclear cell.

Where does cytauxzoon replicate sexually?

Tick

Although exposure to N. caninum is common, clinical disease is uncommon in dogs. Puppies (who were infected transplacentally), on the other hand, can become affected by disease typically at 4 weeks - 6 months of age. What clinical signs can they display?

Transplacental infection of puppies usually leads to myositis and polyradiculoneuritis that initially involves the lumbosacral spi- nal nerve roots. This is manifested as ascending paralysis, muscle atrophy, and fibrous muscle contracture with arthrogryposis (joint contracture), hyperextension of the pelvic limbs, and loss of patel- lar reflexes. Clinical signs progress in some dogs to lethargy, tetraplegia, inabil- ity to fully open the mouth, dysphagia, and respiratory difficulty.

T/F: It is likely that most T. gondii-infected cats and dogs harbor tissue cysts for life. Thus, the presence of serum antibodies is likely to indicate current infection.

True

T/F: Because leishmaniosis has a long incubation period and prolonged disease course, travel-related leishmaniosis in dogs and cats is diagnosed sporadically in regions where sand- fly transmission does not occur

True! Always have it on your list for a patient who has a travel history.

T/F: Dogs with H.americanum have hypoglycemia (40-60 mg/dL) and elevated ALP.

True, they can have an elevated ALP due to the new bone formation (bone isoform). The glucose is usually artifactual due to elevated WBC and excessive utilization.

T/F: The limitation of cytology in dogs for detection of toxoplasmosis is that you cannot differentiate between the tachyzoites of toxoplasmosis and neosporosis.

True. Tis a thing.

What is the causative agent of Chagas' disease?

Trypanosoma cruzi

You acquire the following blood smear samples from a dog who was recently imported from Venezuela. The shelter veterinarian informs you it's having arrhythmias and collapse episodes in the foster's home. What do you see?

Trypomastigotes (blood-borne form of T.Cruzi) n the peripheral blood

What are the clinical signs associated with canine leishmaniosis?

When clinical disease appears, it occurs after a long incubation period (up to 7 years) and varies from mild papular or exfoliative dermatitis to severe disseminated disease due to massive proliferation of histiocytes, B lymphocytes, and plasma cells in reticuloendothelial tissues and immune-mediated consequences of chronic, persistent infection. *Weight loss *Inappetence *Scaling or ulcerative cutaneous lesions *Onychogryphosis (thickening of the claws) *Fever *KCS (leishmaniasis can infect the lacriminal gland) *Uveitis *Severe lymphadenomegaly *Hepatosplenomegaly *ICGN *Lameness due to IMPA

What is the geographical distribution of neospora?

Worldwide

Once ingested by the dog, exposure to ______________ in the intestinal tract results in release of sporozoites, which penetrate the intestinal epithelial wall & transport to the target organs and tissues.

bile