Are Dromedary Camels Susceptible or Non-Susceptible to Foot-and-Mouth Disease Serotype O Soren Alexandersen Danish Institute for Food and Veterinary Research Department of Virology, Lindholm DK-4771 Kalvehave, Denmark SA September 2005 FMD WIDE HOST RANGE Cattle, sheep, goats and pigs African & water buffalo Kudu, impala, warthog, deer Some other animals, including camels, may possibly be infected Man extremely seldom, mild and transient 222
Are Dromedary Camels Susceptible or Non-Susceptible to Foot-and-Mouth Disease Serotype O Experiment 1 Virus: FMDV O UAE 542-99 (WRL O UAE 7/99) isolated in Dubai from minor epithelial lesions from Arabian gazelles. Used as 5th BHK passage Animals: 2 dromedary camels and 2 heifers inoculated subepidermolingually with 10 7.6 TCID 50 Results: Heifers: Clinical disease (relatively mild), viraemia and virus detected in swabs and probangs and development of antibodies Camels: NO clinical disease, NO viraemia, NO virus detected in swabs and probangs and NO development of antibodies Conclusion: no signs of infection in dromedary camels with this inoculum Experiment 2 Contact Inoculated Inoculated Contact Camel Experiment 2 223
Experiment 2 Virus: FMDV O UAE 542-99 (WRL 7/99) as in experiment 1, but prepared from secondary vesicular epithelium from a heifer in experiment 1, i.e. used as 1st cattle passage Animals: 5 dromedary camels (3 naive and 2 from experiment 1) inoculated subepidermo-lingually with 10 7.8 TCID 50, 5 naive dromedary camels as direct contacts and 4 sheep as contacts. Also had 2 sheep kept seperately and inoculated in the coronary band as positive controls. Results: Positive control sheep : Clinical disease (relatively mild), viraemia and development of antibodies. Typical for FMD in sheep. Contact Camels and contact sheep: NO clinical disease, NO viraemia, and NO development of antibodies Inoculated camels: NO clinical disease, but 1/3 naive camels had a one day increase in temperature and developed a viraemia and subsequently antibodies to FMDV. The 2 previously exposed camels from Exp. 1 developed antibodies to FMDV Conclusion: 1 out of 3 inoculated naive camels developed a viraemia but did not transmit infection to contact camels or sheep Experiment 2 - continued Sequencing of virus: Sequenced nearly the complete genome (the L-fragment) of FMDV from the serum of camel 34 at pid 3 (after a single passage in bovine thyroid cells), the inoculum from the heifer and the original 5th BKK inoculum. The virus from the camel is identical to the input virus from the heifer. Interestingly, this virus (from the heifer and from camel 34) is slightly different from the original inoculum, i.e. the 5th BHK passage. The original 5th BHK passage had 8 sequence differences in the L fragment when compared to the two in vivo viruses. Of the 8 differences, 3 were non-coding (2 differences in 2C and 1 difference in 3D). Of the 5 coding differences, 1 is in VP-3 (aa # 158 proline to serine); 2 differences are in VP-1 (aa #13 alanine to threonine and aa # 144 alanine to valine); and 2 differences in 3A at amino acid # 104 (glycine to asparagine) and #129 (alanine to threonine). May potentially have to do with BHK cell culture and subsequent in vivo adaptation as the VP-3 change may reflect on heparan sulphate binding, the VP-1 changes (in particular at aa# 144 just before the RGD motif) may change receptor interaction and the 3A changes may also have to do with adaptation to host cells. Temperature 39,0 38,5 38,0 37,5 37,0 36,5 36,0 35,5 Daily Temperature of FMD treated and control camels Camel 26 (Control) Camel 27 (Control) Camel 28 (Control) Camel 29 (Control) Camel 31 (Control) Camel 30 (Treated) Camel 32 (Treated) Camel 33 (Treated) Camel 34 (Treated) Camel 35 (Treated) 35,0 34,5 34,0-10 -5 0 5 10 15 20 25 30 Days PI 224
Camel Exp. 2 Viraemia Log10 virus or RNA per ml 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 10 14 21 28 Days 532v 537v 34v 532r 537r 34r Dect. lim. V Dect. lim. R Camel Exp. 2 Antibodies 700 532ae 600 537ae 500 34ae Titre 400 300 30ae 33ae 200 100 0 0 1 2 3 4 5 6 10 14 21 28 Days 532av 537av 34av 30av 33av 225
Camel Exp. 2 Antibodies Titre 45 40 35 30 25 20 15 10 5 0 0 1 2 3 4 5 6 10 14 21 28 Days 34ae 30ae 33ae 34av 30av 33av Dect. lim. (50%) Future experiments As experiment 2 has indicated that FMDV serotype O under certain circumstances infect camels (caused viraemia, antibodies and elevated body temperature in 1 out of 3 camels) when using a fully virulent serotype O isolate, it may also be worthwhile to continue these experiments to get better statistical data. Next use 10 naive camels directly inoculated with the heifer 144 type O inoculum - have no contact camels as experiment 2 indicated that contact spread is of no significance. Continue the experiments using FMDV serotype A as this is the other serotype that has been found in the area in or around UAE. An isolate from the region (A SAU 22/92 original epi suspension) from infected cattle material has been agreed upon among Ulli Wernery, Soren Alexandersen and Nigel Ferris/David Paton at the FMD-WRL in Pirbright. Clearly, the preliminary results from experiment 2 suggest that there is much more experimental work to do in order to conclude on the relative, but low, susceptibility of dromedary camels to infection with FMDV. 226
THE END Thanks to Ulli Wernery, Renate Wernery, Peter Nagy, Jutka Juhasz, Anita Varga and Winni Schiele at CVRL, Dubai, colleagues and staff at Pirbright Laboratory and at DFVF- Lindholm, and Gitte Alexandersen, Barup, Denmark Research supported by DFVF as well as by HH General Sheikh Mohammed Bin Rashid Al Maktoum Experiment 1 SUMMARY 5th BHK passage FMDV O UAE 7/99 inoculum 2 dromedary camels and 2 heifers inoculated in the tongue with 10 7.6 TCID 50 Heifers: Clinical disease (relatively mild) and virus and antibody detected Camels: NO clinical disease, NO viraemia, NO virus detected and NO development of antibodies Conclusion: no signs of infection in dromedary camels with this inoculum SUMMARY Experiment 2 FMDV O 7/99 as in experiment 1, but prepared from secondary vesicular epithelium from heifer in experiment 1, i.e. used as 1st cattle passage 5 dromedary camels (3 naive and 2 from experiment 1) inoculated in the tongue with 10 7.8 TCID 50, 5 naive dromedary camels and 4 sheep as contacts. 2 inoculated sheep kept seperately ( positive controls got typical disease, viraemia and development of antibodies). Contact Camels and contact sheep: NO clinical disease, NO viraemia, and NO development of antibodies Inoculated camels: NO clinical disease, but 1/3 naive camels had a one day increase in temperature and developed a viraemia and antibodies. The 2 previously exposed camels from Exp. 1 developed antibodies Original 5th BHK virus had 8 sequence differences in the L fragment compared to the two in vivo viruses. Of 8 differences, 5 were coding differences; 1 in VP-3; 2 in VP-1 and 2 differences in 3A. Conclusion: 1 out of 3 inoculated naive camels developed a viraemia but did not transmit infection to contact camels or sheep 227