Dr. Lucy M Mutharia

Associate Professor | Department of Molecular & Cellular Biology | University of Guelph, Guelph. Ontario. N1G2W1 Canada

Mycobacterium avium subspecies paratuberculosis (MAP), an intracellular pathogen and the causative agent of Johne’s disease (JD, or paratuberculosis) which affects wild and domestic animals worldwide. JD has significant economic impacts and public health concerns. After fecal-oral infection, animals progress through a subclinical phase lasting months to years before development of clinical JD, which is invariably fatal. Subclinical and clinical JD is accompanied by shedding of MAP in feces and milk, which is the primary source of infection for susceptible herdmates. MAP can survive pasteurization and could enter the human food chain through meat, dairy products and untreated water supplies.

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MAP has been associated with human Crohn’s disease although a causal role has not been demonstrated. Therefore, efforts to control JD must detect early infection so that transmission and environmental burden of the bacterium is reduced. Current tests detect late subclinical and clinical infections; however, sensitivity during the early infection is low (15%). Because early intestinal Map infection has been difficult to study, early MAP-specific immunity remains largely uncharacterized. The lack of vaccines that prevent infection and the failure to detect early infection remains the most significant barrier to JD control throughout the world. To address these critical needs, there needs to be better understanding of the biology of MAP, the development of immunity during early intestinal Map infection, and the role of specific MAP components in the immunopathogenesis of JD.

The long-term goal of my research has been an exploration of the pathogen-host interactions with specific focus on the MAP exoproteome (extracellularly secreted proteins) and the discovery of novel diagnostic antigens or assays for detection of subclinical JD. Our recent progress and achievements include: Identifying and characterizing specific exoproteome MAP proteins that elicited cell- and antibody-mediated responses during early infection using an intestinal-loop animal infection model; generating libraries of the recombinant proteins; identifying MAP-specific epitopes in specific proteins for design of serodiagnostic reagents; designing and generating recombinant mixed-epitope peptides for study of the immunopathogenesis of MAP infections. Collectively, my research showed that the MAP exoproteome can be mined for MAP-specific epitopes to detect antibody- and cell-mediated immune responses in subclinical JD, and to identify novel MAP putative virulence factors. 

–          How long have they been working I the field (young and seasoned microbiologists are welcome. We want everyone to know about your work and find out what you are doing)?


I joined the University of Guelph in late 1989. During the last 3 decades I have been lucky to work with many excellent undergraduate and graduate students, technical staff and post-doctoral fellows. We have had excellent collaborations with researchers in the veterinary field and in industry.  Research in my lab has focused in 3 areas: the exploration and understanding of the role of specific components of various bacterial pathogens during infection, identifying and characterizing immunogenic and pathogen-specific antigens, epitopes involved with eliciting antibody- and cell-mediated immune responses, and developing diagnostic (molecular and immunoassays) assays. We have investigated various pathogens including, fish pathogens (Vibrio anguillarum, Vibrio ordalii and Flavobacterium branchiophilum), MAP and Mycobacterium avium, and amoeba as environmental hosts of bacterial pathogens. 


–          How innovative is the work and how does it benefit Africa or people of African origin around the world?

JD is a production-limiting disease which affects domesticated food production ruminant animals (e.g. cattle, goats, sheep, camels) worldwide. Africa is no exception – Sudan, South Africa, Egypt, Kenya, Tanzania, Morocco, Zambia and Zaire (change the Democratic Republic of the Congo, previously called Zaire) have reported cases of JD in cattle, sheep, goats, camels (and even a dog in South Africa) and in water.  There are many factors that hinder the diagnosis of JD including: the similarity of intestinal granulomatous enteritis in JD to that caused by intestinal infections by species of mycobacteria, MAP serological diagnostic tests have low sensitivity (attributed to the extensive antigenic similarities among mycobacteria), and, culture-based detection is complex and expensive. MAP is extremely slow-growing and cultures are easily contaminated by rapidly-growing organisms. Sample (feces, milk) require decontamination to kill rapidly growing organisms and a long period of weeks or several months of incubation before colonies become visible. Identification using molecular-based tests requires multiple steps for lysis of the complex cell wall and the appropriate controls. My research aims to develop better diagnostic reagents and advance understanding of the immunopathogenesis of MAP infections. Towards these goals, we have identified MAP proteins containing MAP-specific epitopes, and epitopes which induced immune responses during early disease stage. These reagents are candidates for development of MAP-specific diagnostic immunoassays.  We are interested in developing assays for rapid detection of MAP-specific antibodies using low-tech visual assays (e.g. the lateral flow immune assay platforms) which can be modified for various non-lab based settings. The availability of rapid, low cost and rapid JD-tests has many benefits for African e.g. enhancing animal welfare, reducing the risk of MAP transmission through contamination of milk and water.      


–          Practical applications of the work they are doing

We have identified MAP-secreted potential that can be used as targets for immunological and diagnostic reagents. These reagents will further our understanding of the biology of MAP infections. MAP-specific epitopes that induce early protective immune responses during early infection are targets for research on vaccine development.  


–          Recent and other relevant Publications (books, journal papers, Review papers)


Use of the bead beater for preparation of Mycobacterium paratuberculosis template DNA in milk. 2001. J Odumeru, A Gao, S Chen, M Raymond and L Mutharia Can. J Vet Res. 65:201-5. PMCID: PMC1189680; PMID: 11768125


Development of improved method for isolation of Mycobacterium avium subsp. paratuberculosis from bulk tank milk: Effect of age of milk, centrifugation, and decontamination. 2005. A Gao, J Odumeru, M. Raymond, and L Mutharia. Can. J Vet Res. 69:81-87. PMID: 15971671

Improved template DNA preparation procedure for detection of Mycobacterium avium subsp. paratuberculosis in milk by PCR.  2007. A Gao, L Mutharia, M Raymond and J Odumeru. J Microbiol. Meth. 69:417-20. https://doi.org/10.1016/j.mimet.2006.10.019

Antibody specificities of polyclonal rabbit and rainbow trout antisera against Vibrio ordalii and serotype 0:2 strains of Vibrio anguillarum. 1993. Lucy M Mutharia, Bonnie T Raymond, Teri R. Dekievit, and Roselynn M. W. Stevenson. Can J Microbiol. 39:492-499.

Mycobacterium avium subsp. paratuberculosis in muscle, lymphatic and organ tissues from cows with advanced Johne’s disease. 2010. LM Mutharia, MD Klassen, J Fairles, S Barbut, CO Gill. International J Food Microbiol. 136:310-44. https://doi.org/10.1016/j.ijfoodmicro.2009.10.026

Novel Secreted Antigens of Mycobacterium paratuberculosis as Serodiagnostic Biomarkers for Johne’s Disease in Cattle. 2013. Antonio Facciuolo, David F. Kelton, Lucy M. Mutharia. Clin Vacc Immunol. DOI: 10.1128/CVI.00380-13.

Mycobacterial glycoproteins: a novel subset of vaccine candidates. 2014. A Facciuolo and LM Mutharia. Front. Cell. Infect. Microbiol., https://doi.org/10.3389/fcimb.2014.00133

Marked Differences in Mucosal Immune Responses Induced in Ileal versus Jejunal Peyer’s Patches to Mycobacterium avium subsp. paratuberculosis Secreted Proteins following Targeted Enteric Infection in Young Calves. 2016. A Facciuolo, PGonzalez-Cano, S napper, PJ Giebel, LM Mutharia. PLoS One. 11(7): e0158747. doi: 10.1371/journal.pone.0158747

Prevalence of Toxoplasma gondii and Other Gastrointestinal Parasites in Domestic Cats from Households in Thika Region, Kenya. 2017. AN Njuguna,JM Kagira, SM Karanja, M Ngotho, L Mutharia, NW Maina. BioMed Res Intern.  https://doi.org/10.1155/2017/7615810

Identification of antigenic proteins from Mycobacterium avium subspecies paratuberculosis cell envelope by comparative proteomic analysis. 2018. S Karuppusamy, L Mutharia, D Kelton, N Karrow, G Kirby. Microbiol. 164 https://doi.org/10.1099/mic.0.000606 


–          Awards won


2017: YWCA/YMCA Guelph Women of Distinction (STEM category)