Tick Research at ILRI
Richard Bishop
8 International Congress on Ticks and Tick-Borne Pathogens (TTP8)
and 12 Biennial Conference, South Africa, 24-29 August 2014

ILRI Tick Unit Workshop
ICTTD Cape Town 2014
• How Does ILRI Reintegrate into
the Global Tick Research Arena?
• How can we better utilise the ILRI
Tick unit -Collaborative projects?
•

ILRI Tick Unit- Tick Species
• Ixodid ticks (9 species)
• Rhipicephalus appendiculatus: 9 stocks
Vector of ECF- differences in vector
competence for Theileria parva
• R. zambeziensis, R.evertsi, R.pulchellus
• Amblyomma variegatum
• A.gemma
• Hyalomma anatolicum
• Boophilus (Rhipicephalus) decoloratus
• B.(Rhipicephalus) microplus

Tick Unit facilities and expertise
• Capacity for 16 cattle experiments for
evaluation of vaccines or acaricides
• Rabbit room with capacity for 48 rabbits
• Salivary gland and other tissue
dissection
• RNAi equipment
• Manager- with an agenda to develop s
bew scientific activities-Naftaly Githaka

Laboratory Capacity
• Advanced Molecular biology
infrastructure
• Next Generation sequencing
- 454 titanium
- Illumina Mi Seq
Library preparation specialist:
Bioinformatics Cluster
Systems Administrator

The First Commercial ‘Anti-Parasite’ Vaccine
TickGard (based on
recombinant BM86 gut
glycoprotein) from
Rhipicephalus (Boophilus)
microplus

BM86 and homologues
• BM86 protects against Boophilus (Rhipicephalus )
decoloratus but not R. appendiculatus
• Homologues cloned from R. decoloratus and R.
appendiculatus-
• In three host tick R. appendiculatus moulting from
nymph to adults was affected
• Protection does not correlate with sequence identity-
Better efficacy with heterologus challenge
• Conserved epitopes identified-Pepscan Hylomma-
Rhipicephalus- Boophilus

ILRI-Evaluation of Unconventional
tick vaccine candidates in cattle
• Cement proteins
• RIM 36-Immunodominant in cattle- no protection
• Trp64-from IxodesPat Nuttall group protects against
human encephalitis virus- no protection in cattle
• Histamine Binding (Lipocalin fold) protein-ambiguous
results

Genomics and Functional genomics for novel
vaccine candidates
• Salivary gland EST databases developed in
collaboration with TIGR
• Amblyomma variegatum
• R.appendiculatus-infected versus uninfected-
Many differences (7000+) low abundance
• Suppression subtractive approach to look for
transcripts up-regulated in infected salivary
glands

Tick Genomics
• Genome organisation.
• Many Transposons
• Novel SINE element
• Allelic exclusion of very distinct RA86
variants in R. appendulatus lab stock
• Development of microsatellite markers
for R. appendiculatus laboratory and
field populations

A Wider Research Agenda
• Recent Review of ILRI tick unit by Peter
Willadsen-Ex CSIRO-recommended inclusion of
novel activities in additional tick species
• Activities related to direct tick control- Evaluating
vaccines and acaricides-Group 1
• Tick-pathogen interaction research-Group2
• Measuring tick burdens and impact –Group 3
Special focus on B. (R) microplus in Africa

ECF recombinant vaccine support
• Sporozoite production
• Tick challenge model-All current work is based on ITM (live
sporozoite and drug administration model)
• Investigate mechanisms of immunity from tick-delivered T. parva
• Tick-sporozoite antigen combination vaccines
• Complexity of challenge scenario-taxonomy of ticks using new
techniques and monitoring pathogen loads

ITM improvement irradiated sporozoite
vaccine
• Irradiated sporozoite vaccine
• Plasmodium-Malaria analogy
• Not fully researched for T. parva
• Interest from Sanaria
• Simplify composition of current vaccine.

Improved tick control
• Novel acaricide evaluation:
- Sigma-Genosys acaricide trial
New Vaccines-
• FER2 evaluation as a vaccine candidate in cattle for
b. microplus
• Participation in wider evaluation of novel candidates
from reverse vaccinology

Acaricide Resistance Monitoring
• In Collaboration with Ministries of Livestock
• Not Well researched in Africa
• Start in East Africa

Tick-Host-Pathogen interface
Theileria parva
Arthropod
vector
Pathogen-Host
Infection of vertebrate host
Role of tick salivary gland factors?
Parasite evasion of vertebrate host
Vertebrate host
(i)
(iii)
(ii)
Pathogen-vector
Pathogen has to overcome tick ‘barriers’:
1. Gut Invasion
2. Tick immune system
3 Salivary gland maturation
Tick- vertebrate host
responses
Prolonged attachment by Ixodid tick:
Tick injects a cocktail of peptides and lipids
Tissue cement to enhance feeding
Inflammatory responses
Immunomodulation
Haemostatic responses

ILRI Nascent Activities for
tick/pathogen interaction
• Two R. appendiculatus genetically related
stocks that differ in vector competence for T.
parva
• Metagenomics- Novel viral pathogen
discovery-Access to African tick species

Livestock Tick distribution and
Impact
• Special focus on Boophilus (Rhipicephalus) in
an African context- This tick is spreading
rapidly in South, East and West Africa
• Test for acaricide resistance not well
monitored in Africa
• What is the direct impact of ticks on livestock
production including milk?

Tick Challenge Model
• Efficacy of anti-pathogen or anti-vector antigens in the
field is difficult to test using a needle challenge in the
laboratory
• Needle challenge is a MODEL SYSTEM
• Therefore an experimental tick challenge system run in
parallel will be very valuable
• Baseline data on tick challenge has been generated at
ILRI using a selected low abundance line-designed to
be more comparable to field challenge

R. appendiculatus salivary gland EST
Data from T.parva infected and
uninfected females
• 18,000+ total sequences RA sequences.
7359 unique-Generated in collaboration with
TIGR.
• No Major clusters qualitatively different
between T. parva infected and uninfected
salivary glands

ILRI research-Combination
sporozoite-tick salivary gland
• T.parva p67 sporozoite antigen better in the
laboratory than the field
• Combine with salivary gland antigens
• Antibody responses can be induced against
seven distinct recombinant antigens P67, and
six salivary gland components

Better lives through livestock
ilri.org
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