NCVP - National Center for Veterinary Parasitology

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  • Home
  • Resources
    • People >
      • Directors and Advisory Board
      • Residents >
        • Boehringer Ingelheim Resident
        • Elanco Resident
        • IDEXX Resident
        • Merck Resident
        • Zoetis Resident
      • NCVP Alums
      • Clinical Parasitology Support
      • Additional Support
      • Sponsors
    • Parasite Image Database >
      • Protozoa
      • Arthropods
      • Nematodes
      • Trematodes
      • Cestodes
      • Acanthocephala
      • Tick-Borne Disease Agents
    • Case of the Month
    • Teaching and Research Materials >
      • Teaching Specimen Request
      • Parasite Jeopardy Games
      • Parasite Videos
    • Online Resources >
      • Parasitology Board Preparation
      • Additional Parasitology Resources
      • Resources for Educators
    • NCVP Board Member Resources
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    • Residents' Corner
  • News
    • Veterinary Parasitology in the News
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  • Opportunities
    • Request for Proposals
    • Grant Portal
    • Residency Application
    • Continuing Education in Parasitology
    • Positions Open in Veterinary Parasitology

Case of the Month

December 2021

 

What is ailing the reindeer? 

A blood sample from a 3.5-year-old female reindeer slightly underweight was submitted for a CBC and a modified Knott’s tests.
Image 1-3: Modified Knott's test.
Image 4: ​
Microfilariae are 140-169 µM in length with a blunt rounded tail and a sheath closely pressed against the body of the microfilariae extends only a short distance beyond the head and tail which makes it difficult to see
What's your diagnosis?
​Rumenfilaria andersoni, is a filarid nematode (Family Onchocercidae, subfamily Splendidofilariinae).  It was firs described from moose (Alces alces) in Ontario, Canada and mistakenly to occur in subserosal veins of the rumen. Adult worms are 55-144 µM in length. In addition to moose, infections have also been reported in reindeer (Rangifer tarandus), white tail deer (Odocoileus virginianus) and roe deer (Capreolus capreolus). Infection in cervids have been reported in Alaska, Ontario and Finland.  It may have been introduced into Finland in imported white-tailed deer from Minnesota donated by Finnish immigrants.

Case and photos provided by Dr. Gary Conboy.

November 2021

 

Winter is coming....

​In November 2020, these ticks were removed from a horse in Oklahoma and submitted to the parasitology lab for identification.
Picture

Images 1-3: Key features for identification.

These ticks are a brown variant of Dermacentor albipictus, or the winter tick, a one-host tick commonly found on horses and white-tailed deer in the southern region of North America. Formerly referred to as D. nigrolineatus, inornate winter ticks can be distinguished from Rhipicephalus spp. by the presence of a rectangular scutum. The ornate variant of D. albipictus more common in northern regions is often found feeding on moose, elk, and deer. In large numbers, D. albipictus contribute to poor condition and death in moose and elk. Winter ticks, as the name suggests, are most active in the fall and winter months, and have been implicated as vectors of Anaplasma marginale and Babesia duncani.
​

What's your diagnosis?

October 2021

 

Dog"ged" microfilariae

​A blood sample from a 21-month old female Boston Terrier Mix, was submitted to the parasitology diagnostic lab to be tested for Dirofilaria immitis detection.  The dog had a history of microfilaremia in 2020 but no antigen was detected during that same year. In September 2021, during the annual wellness a snap test was performed at the clinic with no antigen detected, but microfilaria was again observed on the direct smear.  To rule out the presence of antigen-antibody complexes, the serum sample was heat treated at the diagnostic lab, but no antigen was detected. The Modified Knott’s test showed the presence of the following microfilariae. (Images 1-3) Size average 275 µm in length x 5 µm in width.

Picture

Images 1-3: Key features for identification.

What's your diagnosis?
​
​Acanthocheilonema reconditum, is a member of the subfamily Onchocercinae that infects canids. It is transmitted by fleas and the louse Heterodoxus spiniger. The adults are located in the subcutaneous tissues where they do not cause any pathology. The importance of this parasite lies on the confusion that its microfilariae can create on the diagnosis of Dirofilaria immitis infection. Both microfilariae are similar and can be easily confused, however morphological characteristics and motility can help differentiate these two microfilariae. 
Observing microfilariae in puppies and young dogs with no D. immitis antigen detection can be explained by infection of A. reconditum such as this case or transplacental transmission of D. immitis.

September 2021

 

Not another coughing cat

​A 6-year-old formerly-feral domestic shorthair cat presented to a veterinary internist in Virginia for chronic coughing. Serum antigen and antibody testing for heartworm infection was negative. A fecal sample was collected and submitted to a diagnostic laboratory for evaluation, which revealed the presence of the following parasite ova (Image 1). In addition, thoracic radiographs were taken (Image 2). Based on these results the cat was treated by the internist with weekly fenbendazole and ivermectin, but the parasite persisted in serial fecal exams and recheck radiographs were relatively unchanged.
Picture
Image 1: Ova found on fecal examination (40x objective).
Picture
Image 2: Left lateral radiographic view of thorax. Radiographs demonstrated right middle lung lobe consolidation with heavy bronchial pattern and cavitated lesions.
What's your diagnosis and recommendation?
Paragonimus kellicotti, also known as the lung fluke, is a trematode found throughout North America. The parasite has a 3-host life cycle in which the infective larval stage (miricidium) first penetrates an aquatic snail, where it develops into a cercaria and later exits the snail to encyst within the tissues of crawfish. The life cycle is completed when a vertebrate definitive host (animal or human) consumes a crawfish containing these cysts, and the parasites migrate from the gastrointestinal tract to the lungs where they encyst and reproduce. Eggs are coughed up in sputum, swallowed, and passed into the environment via the host's feces.
Encystment of Paragonimus within the lung parenchyma most often results in the clinical signs of chronic, persistent coughing (in rare cases, rupture of a lung cyst can result in pneumothorax and acute dyspnea). Large cysts may be appreciated on thoracic radiographs as nodular or cavitary lesions, particularly in the right caudal lung lobes. In this case, the paragonimiasis in this cat likely persisted due to an inadequate treatment protocol. Paragonimus treatment differs from that of lung nematodes in that it requires the use of praziquantel (often used in conjunction with a benzimidazole) in order to eliminate the parasite effectively.

August 2021

 

"Acarologic" venture

​In February 2021, this tick was removed from a 4-year-old male castrated Jack Russell Terrier from Texas, and sent to the parasitology lab for identification. The lab worker was able to take pictures showcasing key features for identifying this specimen, as seen below. 
Picture
Image 1: Key features for identification. 
What's your diagnosis?
​This is Ixodes cookei, the groundhog tick or woodchuck tick. Female Ixodes cookei can be differentiated from other Ixodes species based on their angular scutum shape and relatively short palps.  Females of Ixodes scapularis will instead have a rounded, oval shaped scutum, and longer palps, as seen in Image 2 (right).
 
Groundhog ticks are found throughout eastern North America. In northeastern states, the upper Midwest, and eastern Canada, this tick serves as a vector for Powassan virus and may also transmit Borrelia burgdorferi. In Canada, adult Ixodes cookei are most active in the summer but in the southern US this tick is more commonly found in the winter months.
Picture
Image 2: Adult female Ixodes cookei (left) and Ixodes scapularis (right).

July 2021

 

Hooked on you

An adult female 3-year-old greyhound presented to a veterinarian in Illinois for persistent hookworm infection. She had been dewormed monthly with Pyrantel, Febantel, and transdermal Moxidectin for the past 3 months. A fecal sample was collected and a quantitative fecal egg count was performed using a modified McMaster test. The following eggs were found and counted at 850 eggs per gram (Image 1). 
Picture
Image 1: Eggs found on fecal examination (10x objective). 
What's your diagnosis and recommendations?
Multi-drug resistant Ancylostoma caninum is a growing concern and commonly reported in retired racing greyhounds although the issue has also been identified in other breeds of dogs. To confirm multi-drug resistance, a fecal egg count reduction test (FECRT) is performed by collecting samples immediately prior to treatment and again 14 days following treatment. If hookworms are susceptible to the anthelmintic used, a FECRT should show a reduction of >95%. Because this dog has already been dewormed with all three anthelmintic classes, resistance is likely and off-label use of Emodepside can be considered following all appropriate safety and regulatory recommendations (see reference).
 
A FECRT should be performed to confirm efficacy. In addition, centrifugal fecal floats – which are more sensitive than modified McMaster test – should be performed monthly for 3 months to confirm the dog does not become reinfected. During this time, it is important to maintain strict fecal clean-up and avoid dog parks to minimize sources of reinfection until no eggs are consistently seen on fecal analysis.
 
There are 4 routes of transmission for hookworms in dogs: ingestion of infective L3 larvae, direct penetration of larvae percutaneously, transmammary transmission from mother to pups, and ingestion of paratenic hosts containing the infective L3.
 
An event that can be confused with persistent hookworm infection is "larval leak", when encysted larvae migrate from tissues and colonize the small intestine and becoming patent.  Due to this migration, fecal egg counts 14 days after treatment are important. Earlier fecal egg counts may reflect egg suppression following treatment but not true efficacy, and if eggs are present in the feces 21 days or more after treatment, reinfection from the environment or via larval leak is suggested rather than resistance.
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