Ray Kaplan

Department of Infectious Diseases
BS, DVM, PhD, DipEVPC, DipACVM (Parasitology)


  • Infectious Diseases
  • Parasitology


The primary research focus of my laboratory is to measure, understand, and solve the problems presented by drug-resistance in nematode parasites. Over the past half century, the availability of cheap and effective anthelmintic drugs has led to an almost complete reliance on these chemicals for parasite control in animals. Chemical-based parasite control was extremely effective for many years, but we now know that this strategy has turned out to be shortsighted and unsustainable.

Parasite drug resistance is now recognized globally as one of the greatest health threats to grazing livestock, and has recently been demonstrated in heartworms, hookworms, and tapeworms of dogs. Also, in recent years there has been a dramatic increase in the use of mass drug administration to reduce the morbidity associated with helminth infections of humans, raising the likelihood that anthelmintic resistance will become a public health concern in the near future.

To address this problem, my laboratory pursues research projects with several different areas of emphasis:

  • Developing in vitro and molecular diagnostic assays to detect anthelmintic resistance in nematode populations
  • Studying the molecular biology and population genetics of anthelmintic resistance
  • Studying and developing novel and sustainable approaches to parasite control that rely less heavily on chemical anthelmintics
  • Studying host-parasite interactions and the mechanisms of action and resistance of anthelmintics
  • Measuring the prevalence of drug resistance using both in vitro and in vivo assays

Historically, most of our research has focused on nematode parasites of livestock; however, more recently we have initiated research projects investigating similar issues in dog [heartworms (D. immitis) and hookworms (Ancylostoma caninum)], and nematode parasites of poultry.

We are also involved in studies investigating novel and sustainable approaches to nematode parasite control. In the past, most of this work has been conducted with sheep and goats under the auspices of the American Consortium for Small Ruminant Parasite Control in collaboration with a multi-disciplinary team of veterinarians, scientists, and small ruminant extension specialists from institutions throughout the southern United States as well as the University of Pretoria and the Onderstepoort Veterinary Institute in South Africa.

An important new tool originally developed in South Africa for the control of Haemonchus contortus is the FAMACHA© method for identifying anemic animals in need of treatment. Using this method, a targeted selective treatment program can be instituted. This approach allows farmers to identify those animals in need of treatment, but also those that do not need treatment. Thus parasites are controlled, while at the same time refugia levels are managed, thereby reducing the selection pressure for drug resistance. Since its introduction in the US in 2003, FAMACHA© has been warmly embraced by farmers, and recent surveys of farmers trained in FAMACHA© suggest it is making an important impact. The Kaplan lab is the distributor for the FAMACHA© anemia color charts in the U.S. (under the auspices of the American Consortium for Small Ruminant Parasite Control), with Dr. Kaplan serving as director of the U.S. FAMACHA© program. Visit the Consortium (ACSRPC) website ( or email us ( for more information.

Our laboratory also maintains constant surveillance for the detection of new occurrences of anthelmintic resistance (and multiple-drug resistance) in parasites that have not been recognized previously to be drug-resistant (and/or multiple-drug resistant) in the U.S.

Lastly, our laboratory maintains both drug-susceptible and drug-resistant isolates of several different nematode parasites, and these are available to others as a resource for research.

Research Interests

  • Biology, molecular mechanisms, and population genetics of anthelmintic resistance in nematode parasites
  • Biology, epidemiology, and control of gastrointestinal parasites of ruminants, horses, and poultry
  • Biology, epidemiology, and treatment of heartworm (Dirofilaria immitis) and hookworms (Ancylostoma caninum) in dogs with special emphasis on factors involved with the development and spread of anthelmintic resistance
  • Development and optimization of diagnostic assays for detecting resistance to anthelmintics in nematode parasites

Educational Background

  • ​BS (1983), Virginia Polytechnic Institute and State University
  • DVM (1988), Virginia-Maryland Regional College of Veterinary Medicine
  • PhD (1995), University of Florida, College of Veterinary Medicine
  • Diplomate, European Veterinary Parasitology College
  • Diplomate, The American College of Veterinary Microbiologists (Parasitology)

Selected Publications

My Bibliography – NCBI

Search PubMed for “Kaplan, Ray”

    • Kaplan, R.M., T.R. Klei, E.T. Lyons, G.D. Lester, D.D. French, S.C. Tolliver, C.H. Courtney, Y. Zhao, and A. Vidyashankar. 2004. Prevalence of anthelmintic resistant cyathostomes on horse farms. JAVMA, 225(6): 903-910.


    • Kaplan, R.M., J.M. Burke, T.H. Terrill, J.E. Miller, W.R. Getz, S. Mobini, E. Valencia, M.J. Williams, L.H. Williamson, M. Larsen, and A.F. Vatta. 2004. Validation of the FAMACHA© eye color chart for detecting clinical anemia in sheep and goats on farms in the southern United States. Veterinary Parasitology 123: 105-120.


    • Kaplan, R.M. 2004. Drug resistance in nematodes of veterinary importance: a status report. Trends in Parasitology 20(10): 477-481. [Identified by Essential Science Indicators to be one of the most cited papers in the research area of “DRUG RESISTANCE.”]


    • Tandon, R., K.T. LePage, and R.M. Kaplan 2006. Cloning and characterization of genes encoding α and β subunits of glutamate-gated chloride channel protein in Cylicocyclus nassatus. Molecular and Biochemical Parasitology, 150:46-55.


    • Schwenkenbecher, J.M., M. Albonico, B. Quentin, R.M. Kaplan. 2007. Characterization of beta-tubulin genes in hookworms and investigation of resistance-associated mutations using real-time PCR. Molecular and Biochemical Parasitology, 156:167-174.


    • Nielsen, M.K., D.S. Peterson, J. Monrad, S.M. Thamsborg, SN. Olsen, R.M. Kaplan. 2008. Detection and semi-quantification of Strongylus vulgaris DNA in equine faeces by real- time PCR. International Journal for Parasitology, 38:443-453.


    • Howell, S.B., J.M. Burke, J.E. Miller, T.H. Terrill, E. Valencia , M.J. Williams, L.H. Williamson, A.M. Zajac, R.M. Kaplan. 2008. Anthelmintic resistance on sheep and goat farms in the southeastern United States, JAVMA, 233(12):1913-1919


    • Kaplan, R. M. and M. K. Nielsen. 2010. An evidence-based approach to equine parasite control: It ain’t the 60s anymore, Equine Veterinary Education, 22 (6) 306-316


    • Kaplan, R.M. and A.N. Vidyashankar, 2012. An inconvenient truth: global worming and anthelmintic resistance, Veterinary Parasitology, 186:70-78.


    • Diawara, A., Schwenkenbecher, J.M., Kaplan, R.M., and Prichard, R.K., 2013. Molecular and biological diagnostic tests for monitoring benzimidazole resistance in human soil-transmitted helminths, AJTMH, 88(6): 1052-61.


    • B.E. Storey, C. Marcellino, M. M. Miller, M. J. Maclean, E. Mostafa, J.S. Howell, J. Sakanari, A. J. Wolstenholme, R.M. Kaplan. (2014) Utilization of computer processed high definition video imaging for measuring motility of microscopic nematode stages on a quantitative scale: “The Worminator”, International Journal for Parasitology: Drugs and Drug Resistance, 4 (3): 233-243.


    • A.W. Park, J. Haven, R.M, Kaplan, S. Gandon. (2015) Refugia and the evolutionary epidemiology of drug resistance. Biology Letters. 11 (11) DOI: 10.1098/rsbl.2015.07.


    • A.N. Vidyashankar, P.D. Jimenez Castro and R.M. Kaplan. (2017) A Statistical Approach for Evaluating the Effectiveness of Heartworm Drugs: What Does 100% Efficacy Really Mean? Parasite and Vectors, 10(Suppl 2):516: 97-108.


    • M.M. George, L. Lopez-Soberal, B.E. Storey, S.B. Howell, R.M. Kaplan. (2018) Inhibition of motility in the L3 stage is a poor phenotype for detecting and measuring resistance to avermectin/milbemycin drugs in gastrointestinal nematodes of livestock, International Journal for Parasitology: Drugs and Drug Resistance, 8(1):22-30.


    • K.L. Paras, M.M. George, A.N. Vidyashankar, R.M. Kaplan. (2018) Comparison of fecal egg counting methods in four livestock species, Veterinary Parasitology, 257:21-27.


  • B. Levecke, R.M. Kaplan, S.M. Thamsborg, P.R. Torgerson, J. Vercruysse, R.J. Dobson. (2018) How to improve the standardization and the diagnostic performance of the fecal egg count reduction test? Veterinary Parasitology, 253:71-78