role of buffalo in the maintenance of foot-and-mouth ......3 knp buffalo isolates sat1/knp/196/91...

Role of buffalo in the maintenance of

foot-and-mouth disease virus

Bryan Charleston

Study design

Institute for Animal Health

3 KNP buffalo isolatesSAT1/KNP/196/91SAT2/KNP/19/89SAT3/KNP/1/08/3

SAT-1

SAT-2

SAT-3

6 month old Nguni cattle (n = 4)

PK cells OVI cattle titration

≈ 1 × 104 TCID50

Skukuza buffalo challenge study≈ 5 × 105 TCID50

N = 16 FMD free buffalo (7♂9♀)

10 – 30 months oldImfolozi Game Reserve, KZN

35DPC

N = 4♀

95DPC 156DPC 163DPC 185DPC 299DPC 400DPC

Necropsy N = 4 buffalo

ACTH stimulation (Synacthen®)N = 4 buffalo

1.25IU/kg 1.25IU/kg




Day 302 Progesterone IUDEstrumate

Acute FMD: naïve buffalo

1DPC

2DPC

Acute FMD: naïve buffaloConclusion• SAT co-infection in cattle – severe clinical FMD• 10 × dose in naïve buffalo:

• mild clinical FMD • integrin αvβ6 expression in tissues typically associated with FMD lesions• viraemic for at least 5 to 7 days• No leucopenia• High levels type 1 IFN• seroconverted to all three serotypes by day 14

3D primer and probe SAT1 primer and probe

SAT2 primer and probeSAT3 primer and probe


Budras, Bovine Anatomy

Follicles with central crypt

Casteleyn et al.,

M Hofmeyr

Chronic FMD: buffalo


Chronic FMD: buffalo

*One round VI only() = passage number on IBRS cells

Virus isolation (IBRS cells)

Day post challenge

Nu

mb

er

of

bu

ffalo

50 DPC 109 DPC 126 DPC 136 DPC 155 DPC 162 DPC 168 DPC 172 DPC 185 DPC

0

1

2

3

4

5

6

7

8Right tonsil swab

Probang

*35

35


Chronic FMD: buffalo3D primer and probe SAT1 primer and probe

SAT2 primer and probeSAT3 primer and probe


10µm

100µm100µm

10µm

Anti-3B (D5) IB11 Merge

Chronic FMD: buffalo95DPC


Discussion points• Despite close contact, +ve virus isolation and ACTH stim – no transmission/ seroconversion in cattle!• Consistent with previous reports:

• no transmission/ transmission only after months of contact• Rx buffalo dexamethasone (Gainaru et al., 1986)

• Rx cattle dexamethasone for 3 weeks (Ilott et al., 1997) – inhibited shedding of FMDV• Co-infection cattle rinderpest/ bovine herpes 1 viruses (McVicar et al., 1977) – no increase virus

recovery/ transmission• Pattern of transmission from captive buffalo during acute infection is also variable

• same pen: buffalo to buffalo/ buffalo to cattle× (Gainaru et al., 1986)/ buffalo to cattle× (Dawe et

al., 1994)

• adjoining pen: buffalo to impala× (Gainaru et al., 1986)

Knowledge gaps and questions• Improved methods to isolate virus/ viral sequences from carrier buffalo• Indentify sites of virus localisation and replication in buffalo• Propose hypothesise for mechanisms of persistence• Test potential “triggers” for transmission: short term stress? Long term stress? “childhood epizootic”?• How infectious are buffalo during acute infection? Virus excretion compared cattle/sheep/pigs. Transmission despite no/ limited FMD lesions?

FMD: buffalo

• FMDV maintains high force of infection in buffalo herds > 98% buffalo in KNP exposed to all three SAT serotypes by age 2 (Thomson, 1992) High rate of infection suggests common mechanism for inter-annual perpetuation Avoids auto-extinction small isolated herds

• Crucial that we understand how FMDV persists in isolated buffalo herds Primary objective to identify triggers to affect transmission from carriers. If we can’t even understand this - how understand in livestock, large populations, global, multiple

serotypes?

• 3 year longitudinal study of isolated breeding herd in KNP– Account for environmental factors absent from experimental studies– Identify factors affecting FMDV status (age, sex, seasonal, co-infections etc.)– Phylogenetic and antigenic phenotype analysis of FMDV isolates– Establish infection parameters in buffalo calves (naïve population)– Test triggers under experimental conditions

• We hypothesise:– Previous demonstration of FMDV particles in lymph tissue on germinal centre FDCs provides a means of

delayed viral clearance (extracellular reservoir)

• To affect transmission:– Immune stimulation (enhance immune-complexed FMDV replication in Fc receptor expressing cells)– Or suppress antibody response – for example protein-calorie restricted diet (Watson, 1985)

Future work

Markus Hofmeyr

Peter Buss

Jenny Joubert

Lin-Mari de Klerk Lorist

Roy Bengis

Louis van Schalkwyk

At Dekker

Scalk van Dyk

Dave Cooper

Francois Maree

Berry Mutowembwa

Brenda Botha

Livio Heath

Katherine Scott

Pamela Opperman

Belinda Blignaut

Ferran JORI, Cirad

Mammal Research

Institute University of

Pretoria

Ivan Morrison

Dan Haydon

Acknowledgments

Nick Juleff

role of buffalo in the maintenance of foot-and-mouth ......3 knp buffalo isolates sat1/knp/196/91...

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