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Serological survey in Libya to assess FMD viruses circulation and vaccine immune response Emiliana Brocchi, Santina Grazioli, Giovanna Dho, Ibrahim Eldaghayes, Abdunaser Dayhum, Abdulwahab Kammon, Monier Sharif and Giancarlo Ferrari

Name of the presenter: Giancarlo Ferrari

Understanding epidemiology (PCP stage 1) surveillance design – IZS Brescia-IZS Rome, Libyan authorities, EuFMD

IZSLER support to:

– Serological testing (country serosurvey)

– Virological diagnosis (FMD suspects confirmation)

– Lab Training (4 vets, June)

– Supply of diagnostic kits

COOPERATION with LIBYA

supported by Italian MINISTRY OF HEALTH

Laboratory diagnostic capacity in Libya

Component 1: investigations in FMD suspected

outbreaks to detect circulating strains.

Component 2: immune response of vaccinated animals.

Component 3: serology as a mean to investigate on the

level of FMD virus circulation (anti-NSP antibodies) and

on the serotypes present (anti-SP serotype-specific

antibodies)

COOPERATION with LIBYA

supported by Italian MINISTRY OF HEALTH

Immune response of vaccinated animals.

• Criteria: The outcome to be measured was the level of NSP and SP antibodies before the vaccine is injected and the level of antibodies at 30 dpv in animals between 6 and 12 months of age (providing animals would have remained NSP negative).

Component 2

Serology as a mean to investigate the level of FMD

virus circulation (anti-NSP antibodies) and on the

serotypes present (anti-SP serotype-specific

antibodies)

• Criteria: LARGE RUMINANTS: For cattle (and buffaloes)

a random selection of 300 owners for each of the

Western and Eastern region and from each of the

randomly selected owner all animals belonging to age-

category 6-18 months was supposed to be sampled.

Component 3

• SMALL RUMINANTS: the target for the small ruminants population were sheep with a random selection of 30 owners for each of the three main regions of Lybia.

– Criteria for being enrolled in the study was to have more than 100 individual heads in their flock. For each flock a total of 48 blood samples were collected divided into the following age-categories: (i) 16 samples from the 6-12 months age group; (ii) 16 from animals between 1 and 2 years of age and (iii) 16 from animals with more than 2 years of age.

Component 3

Of the three serotypes O, A and SAT2 reported in Libya,

type O has been the only one to be detected from

tissue samples in FMD clinical outbreaks in cattle with

the new emergent of the Indian strain O/ME-SA/Ind-

2001 for the first time in North Africa in 2013.

Results - component 1

• Immune response in SR (NSP negative)

Results - component 2

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<10 10-30 30-90 90-180 180->810

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Range of Titres

SR FMDV type O

before vacc. 30 days PV

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<10 10-30 30-90 90-180 180->810

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before vacc. 30 days PV

• Immune response in LR (NSP negative)

Results - component 2

Total number of cattle sampled and tested: 1273

Total number of small ruminants sampled and tested:

2542

Period of sampling: January-May 2013

Vaccination period: November-December 2012 (cattle

with trivalent O, A, SAT2 and small ruminants against

O, A)

Results - component 3

Overall crude prevalence (large ruminants):

P (NSP+) = 235/1273 (18.46%)

P (Type O+) = 766/1273 (60.17%)

P (Type A+) = 825/1273 (64.81%)

P (Type SAT2+) = 548/1273 (43.05%)

Results - component 3

Overall crude prevalence (small ruminants):

P (NSP+) = 371/2542 (14.59%)

P (Type O+) = 1324/2542 (52.08%)

P (Type A+) = 1337/2542 (52.6%)

P (Type SAT2+) = 146/2542 (5.74%)

Results - component 3

Three main questions to be answered:

Data support the hypothesis of endemicity?

Is there any indirect evidence of type A or SAT2 virus

circulation?

Can the level of immunity induced by vaccination be

considered adequate?

Prevalence of NSP+ in small ruminants by age-group:

p (0_12 months) = 26/645 (4.03%) avg age 8.8 months

Lower limit 1.07% - Upper limit 6.99% [DEFT 1.95]

p (12_24 months) = 103/739 (13.93%) avg age 19.8 months

Lower limit 7.43% - Upper limit 20.44% [DEFT 2.60]

p (> 24 months) = 184/785 (23.44%) avg age 47.9 months

Lower limit 14.89% - Upper limit 31.99% [DEFT 2.88]

A similar pattern was observed in each region of Libya

Serological findings (component 3)

• In small ruminants antibodies against SAT2 were found in 5.74% (146/2542) of the animals tested.

• Study of the association between being positive for serotype SAT2 and serotype A and O respectively (through estimation of stratified Odds Ratio)

Evidence of SAT2 virus circulation

Evidence of SAT2 virus circulation (in SR)

Stratified Odds Ratio O vs SAT2 Stratified Odds Ratio A vs SAT2 Among A+ = 4.93 Among O+ = 1.58 Among A- = 4.61 Among O- = 1.48 No modification effect No modification effect Odds Ratio (Mantel-Haenszel) = 4.80 Odds Ratio (Mantel-Haenszel) = 1.56 95% CI for ORmh = 8.54 – 2.70 95% CI for ORmh = 2.58 – 0.95

Identification of serotypes present by serology

REGION ZONE SPECIES FARM N.

NSP +

MEAN TITRES O

MEAN TITRES A

MEAN TITRES SAT2

EVIDENCE for serotype

Alzawia Alzawia City C 27 34 205 7 A

Subrata C 5 211 488 9 A ?

Benghazi

Ajdabiya SR 39 309 19 1 O

Al Abyar

SR

A 20 316 40 7 O

B 9 34 480 6 A

C 9 1660 97 8 O

Benghazi SR 77 207 11 2 O

Suluq SR 13 99 9 2 O

Green Mountain

Al Bayda SR 16 81 209 2 A ?

Almarig C 34 72 100 20 ??

Shahhat C 11 33 38 10 ??

Tobruk SR 24 900 97 3 O

Al Qubbah C 10 50 32 1 ??

Al Sahel C 16 94 50 8 ?

Tripoli

Masallatah SR 27 657 177 4 O

Misratah C 15 48 50 4 ??

Misratah SR 18 31 157 1 A

Tarhunah SR 12 106 623 1 A

Tripoli C 34 84 94 9 ??

Tripoli City C 19 172 50 19 O ?

West Mountain

Az Zintan SR 5 26 3328 2 A

Gharyan SR 22 405 278 2 O ?

Mizdah SR 17 36 859 1 A

Yafran SR 17 532 77 1 O

Color code

Pink POS O Titre vs type O 10X higher

Blue POS A Titre vs type A 10X higher

1. The serconversion rate and the mean antibody titres at 30 DPV was considered to be adequate.

2. Test results on NSP antibodies level suggest a level of endemicity at low rate. In the small ruminant population there is a gradient in the proportion of positives among the three age-categories considered. The hypothesis (to be worked out) is then that the virus is maintained into the small ruminant population (the ratio between small ruminants and large ruminants is around 30. Approximately 6,000,000 of small ruminants vs 200,000 large ruminants).

Conclusions

3. The data available from the survey suggest that the positive results against SAT2 obtained in small ruminants (small ruminants were not vaccinated against SAT2) may be the result of a significant association with being positive also for O

4. Concurrent circulation of serotype A cannot be ruled out

Conclusions

aerial photograph ’90s

IZSLER site

THANKS !!