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Appendix 40

FMD and camelids: International relevance of current research

U. Wernery Central Veterinary Research Laboratory, P.O. Box 597, Dubai, U.A.E.

Key words: Tylopoda, camelids, FMD Abstract Camelids regurgitate and re-chew their food and thus technically ruminate. In strict taxonomic terms, however, they are not recognized as belonging to the suborder Ruminantia. They belong to the suborder Tylopoda. Numerous differences in anatomy and physiology justify a separate classification of tylopods from ruminants. Many reports show that New World Camelids (NWC) and Old World Camelids (OWC) possess a low susceptibility to foot and mouth disease (FMD), and do not appear to be long-term carriers of the foot and mouth disease virus (FMDV). Recent preliminary results from Dubai have shown that two dromedaries infected subepidermolingually with FMD serotype 0 did not develop any clinical signs and failed to develop any lesions at the inoculation site. Infectious FMDV or FMDV RNA were not isolated and the two dromedaries failed to seroconvert. It would, therefore, appear appropriate for OIE to refine the definition of NWC and OWC by clearly stating that these animal species are not members of the suborder Ruminantia. Furthermore, these recent results suggest that dromedaries (and most probably all camelid species), which are listed in the OIE Code chapter as being susceptible to FMD similar to cattle, sheep, goats and pigs, are much less susceptible or non-susceptible to FMD. Therefore, the importance of FMD in camelids should be re-assessed. The Central Veterinary Research Laboratory (CVRL) in Dubai, U.A.E., offers to become a reference laboratory for OWC. For more than a decade, CVRL has published in excess of 150 scientific papers and three reference books on camel diseases. Classification, population and distribution Although camelids ruminate, they are not modified ruminants in a taxonomic sense. A separate evolutionary history of 35 – 40 million years divides tylopods from ruminants. Camelidae belong to the suborder Tylopoda (Fowler, 1997; Table 1). Numerous anatomical and physiological differences justify the separate classification of Tylopoda from Ruminantia. The most important differences are shown in Table 2 and some are explained in several figures. The camelid stomach system differs from that of ruminants. There are only three distinct forestomachs compared to four in ruminants. In camelids they are called compartments (C) 1, 2 and 3. The rumen equivalent is C1, which possesses cranial and caudal glandular sacs. These were once considered to represent the water store of the animal; however they mainly function as absorption and fermentation areas as well as zones of enzymatic secretion (Wilson, 1989). The second, much smaller compartment C2 is the reticulum equivalent, and the eolongated C3 is the combined omasum/abomasun equivalent, which might best be referred to as the tubular stomach due to its length. Compartments 1 and 2 are lined with non-papillary smooth epithelium (Figure 1). In camelids, the motility patterns are markedly different compared with ruminants. Another distinguished feature of all Camelidae is the unique structure of their feet (Fig. 2). The padded feet act like snowshoes allowing them to walk over soft, loose sand without sinking. Camelids walk on thick pads consisting primarily of fat. They possess two digits, and their second and third phalanges are horizontal. The reproductive physiology of camelids is of particular interest. Camels mate in a crouching position (Fig. 3) and while mating the bull exteriorises its “doula” (Fig. 4), a bright pink inflatable sac, to attract females. Camels are induced ovulators. Their gestation period lasted 13 months. A slippery surface of a third membrane surrounding the fetus eases its birth (Figure 5). Latest osteological investigations on post-cranial skeletons of Camelus dromedarius and C. bactrianus have shown that they derived from two different ancestors. Approximately twenty million OWC exist, of which two million are Bactrians (Table 3). There are four different species of NWC which inhabit the high altitudes in South America. The estimated population of NWC is shown in Table 4. Llamas and alpacas were domesticated 7.000 years ago; the dromedary and the Bactrian around 5.000 years ago. Guanacos and vicuñcas are wild and there are few wild Bactrians which roam in the Chinese and Gobi desert. There are no wild dromedaries anymore. The distribution of OWC is shown in Figure 6.

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The knowledge of the susceptibility and resistance to infectious and parasitic diseases is of paramount importance in an area where tylopods mix with other livestock. Review of findings on FMD in camelids FMD remains the single most important animal disease, and OWC and NWC inhabit countries in North and East Africa, the Middle and Far East as well as in South America where FMD is endemic. It has been reported that dromedaries can contract the disease following experimental infection and via close contact with FMD diseased livestock, yet do not present a risk in transmitting FMD to susceptible animals (Kitching, 2002). Summarised results are presented in the following Tables 5 to 8 (Wernery and Kaaden, 2004). Only two reports exist of a natural infection. The execution of experimental infections is poor, and therefore conclusions are questionable. FMD serology and infection in Bactrian camels remains questionable, with FMD diagnosis only being made by means of clinical observations. Results of recent FMD experiments in dromedaries in Dubai with serotype 0

Two Holstein heifers of around 150 kg (6-8 months of age) and two castrated male dromedaries (Camelus dromedarius) around 400-450 kg (7-10 years of age) were each inoculated subepidermo-lingually with 107.6 Tissue Culture Infectious Doses 50% (TCID50) of foot-and-mouth disease virus (FMDV) type O UAE 7/99 in a volume of 0.5 ml (Fig. 7). While the heifers developed elevated body temperatures, were drooling saliva and had typical vesicular lesions (Fig. 8) on the tongue within 24 hours, the two dromedaries did not show any clinical signs of disease and had no vesicular lesions, even at the inoculation site. Infectious FMDV and FMDV RNA were detected at relatively high levels in sera and nasal and mouth swabs from the heifers, but no infectious FMDV or FMDV RNA were isolated in similar samples from the two dromedaries (Fig. 9). Furthermore, the two dromedaries did not develop any detectable antibodies to FMDV. Based on the overall results obtained, we conclude that dromedaries (Camelus dromedarius) are not susceptible to infection with this isolate of FMDV (Wernery et al., 2005). Conclusion Camelids belong to the suborder Tylopoda; they are not ruminants. Camelids possess a low flow susceptibility to FMD, and do not appear to be long-term carriers of the FMDV. These are the main two reasons to remove them from the OIE chapter as possessing the same degree of susceptibility as cattle, sheep and goats. References Abou Zaid, A.A., 1991. Studies on some diseases of camels. PhD Thesis, Faculty of Veterinary Medicine Zagazig, Egypt Farag, M.A., Al-Sukayran, A., Mazlou, K.S, Al-Bokney, A.M., 1998. The susceptibility of camels to natural infection with foot and mouth disease virus. Assiut Veterinary Medical Journal 40, 201 – 211 Fowler, M. E. (1997), Evolutionary history and differences between camelids and ruminants, J. Camel Pract. and Research 4 (2), 99 – 105 Hafez, S.M., Farag, M.A., Al-Mukayel, Al, 1993. Are camels susceptible to natural infection with foot and mouth disease virus? Internal Paper: National Agriculture and Water Research, Center Riyadh, Saudi Arabia Hedger, R.S., Barnett, I.T.R., Gray, D.F., 1980. Some virus diseases of domestic animals in the Sultanate of Oman. Tropical Animal Health and Production 12, 107 –114 Kitching, P. (2002). Identification of foot and mouth disease virus carrier and subclinically infected animals and differentiation from vaccinated animals. Revue scientifique et technique. Foot and mouth disease: facing the new dilemmas. OIE 21 (3), 531 - 538 Kumar, A., Prasad, S., Ahuja, K.L., Tewari, S.C., Dogra, S.C., Garb, D.N., 1983. Distribution pattern of foot and mouth disease virus types in North-West India (1979 – 1981). Haryana Veterinarian 22, 28 – 30 Metwally, M.A., Moussa, A.A., Reda, J., Wahba, S., Omar, A., Daoud, A., Tantawi, H.H., 1986. Detection of antibodies against FMDV in camels by using fluorescent antibody technique. Agricultural Research Review 64, 1079 – 1084 Moussa, A.A., Daoud, A., Tawfik, S., 1979. Susceptibility of camel and sheep to infection with foot and mouth disease virus. Agricultural Research Revision Egypt 57, 1 –19 Moussa, A., Nasser, M.I., Mowafi, L., Salah, A., 1986a. Occurrence of foot and mouth disease in different species of mammals at Sharkia province. Journal of Egypt Veterinary Medicine Association 40, 23 – 35

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Moussa, A.A., Tantawi, H.H., Metwally, N.A., Wahba, S., Hussein, K., Osman, O.A., Saber, M.S., 1986b. Pathogenicity of foot and mouth disease virus isolated from experimentally infected camels to susceptible steers. Agricultural Research Review 64, 1071 – 1077 Moussa, A.A.M., Daoud, A., Omar, A., Meetwally, N., El-Nimr, M., McVicar, J.W. 1987. Isolation of foot and mouth disease virus from camels with ulcerative disease syndromes. Journal of Egypt Veterinary Medicine Association 47, 219 – 229 Moussa, A.A.M., 1988. The role of camels in the epizootiology of FMD in Egypt. In: FAO. The Camel: Development Research. Proceedings of Kuwait Camel Seminar, Kuwait, Oct. 20 – 23, 1986, pp. 162 – 173 Moussa, H.A.A., Youssef, N.M.A., 1998. Serological screening for some viral diseases antibodies in camel sera in Egypt. Egypt Journal of Agricultural Research 76, 867 – 873 Nasser, M., Moussa, A.A., Metwally, M.A., Saleh, R.EL.S., 1980. Secretion and persistence of foot and mouth disease virus in faeces of experimental infected camels and ram. Journal of Egypt Veterinary Medicine Association 40, 3 – 13 Paling, R.W., Jerset, D.M., Heath, B.R., 1979. The occurrence of infectious diseases and mixed farming of domesticated and wild herbivores and domesticated herbivores including camels, in Kenya I. Viral diseases: a serological survey with special reference to foot and mouth disease. Journal of Wildlife Diseases 15, 351 – 359 Richard, D., 1979. Etude de la pathologie du dromedaire dans la souprovence du Borana (Ethiopie) (Study of the pathology of the dromedary in Borana Awraja, Ethiopia). These Doctorales Veterinaire, Paris No. 75, pp. 181 – 190 Wernery, U. and O.-R. Kaaden (2002). Infectious diseases in camelids, Blackwell Science, pp. 3 –17 Wernery, U. and O.-R. Kaaden (2004). Foot-and-mouth disease in camelids: a review, The Veterinary Journal Wernery, U., P. Nagy, C. M. Amaral-Doel, Z. Zhang and S. Alexandersen (2005). Dromedaries (Camelus dromedarius) appear not to be susceptible to infection with foot-and-mouth disease virus serotype 0, The Vet. Rec. (in press) Wilson, R. T. (1989). Ecophysiology of the camelidae and desert ruminants, Springer Verlag, pp. 96 – 98

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Table 1: Classification of camelids and other artiodactylids (Wernery and Kaaden, 2002) Class Mammalia

Order Artiodactyla

Suborder Suiformes Hippopotamuses, swine, peccaries

Suborder Tylopoda Camelids

Old Camelus dromedarius – dromedary camel

World Camelus bactrianus – Bactrian camel

Lama glama – llama

New Lama glama – llama

World Lama pacos – alpaca

Lama guanicoe – guanaco

Vicugna vicugna – vicuña

Suborder Ruminantia Cattle, sheep, goats, water buffalo, giraffe, deer, antelope, bison

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Table 2: Differences between camelids and ruminants Camelids Ruminants Evolutionary pathways diverged 40 million years ago

Evolutionary pathways diverged 40 million years ago

Blood Blood

• red blood cells elliptical and small (6.5 µ)

• predominant white blood cell is the neutrophil

• red blood cells round and larger (10 µ)

• predominant white blood cell is the lymphocyte

Foot • has toenails and soft solar pad • second and third phalanges are

horizontal

Foot • has hooves and sole • second and third phalanges are

nearly vertical Digestive System Digestive System

• foregut fermenter, with regurgitation, re-chewing and re-swallowing

• stomach – 3 compartments (C1-3), resistant to bloat

• compartment 1 and 2 have stratified squamous epithelium

• 2 glandular sacs in C1, act as “reserve water tanks”

• same (parallel evolution) • stomach – 4 compartments,

susceptible to bloat • rumen has papillary epithelium • no glandular sacs

Reproduction Reproduction • induced ovulator • no oestrus cycle • follicular wave cycle • copulation in prone position • diffuse placentation • epidermal membrane surrounding

fetus • cartilaginous projection on tip of

penis • ejaculation prolonged

• spontaneous ovulation • oestrous cycle • no follicular wave cycle • copulation in standing position • cotyledonary placentation • no epidermal membrane surrounding

fetus • no cartilaginous projection on tip of

penis • ejaculation short and intense

Urinary • smooth and elliptical kidney • suburethral diverticulum in female at

external urethral orifice • dorsal urethral recess

Urinary • smooth or lobular kidney • no suburethral diverticulum • dorsal urethral recess in some

species

Parasites • unique lice and coccidia • share some gastrointestinal

nematodes with cattle, sheep and goats

Parasites • unique lice and coccidia • share gastrointestinal nematodes

Infectious diseases • minimally susceptible to tuberculosis • bovine brucellosis is rare • mild susceptibility to foot-and-mouth

disease • rarely develop clinical disease

following exposure/inoculation with other bovine and small ruminant viral diseases

Infectious diseases • Highly susceptible to tuberculosis,

bovine brucellosis and foot-and-mouth disease

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Table 3: Old World camel population in Africa and Asia

Africa Camel

Population Asia

Camel

Population

Algeria 150,000 Afghanistan 270,000

Chad 446,000 India 1,150,000

Djibouti 60,000 Iran 27,000

Egypt 90,000 Iraq 250,000

Ethiopia 1,000,000 Israel 11,000

Kenya 610,000 Jordan 14,000

Libya 135,000 Kuwait 5,000

Mali 173,000 Mongolia 580,000

Mauritania 800,000 Oman 6,000

Morocco 230,000 Pakistan 880,000

Niger 410,000 Qatar 10,000

Nigeria 18,000 Saudi Arabia 780,000

Senegal 6,000 Syria 7,000

Somalia 6,000,000 Turkey 12,000

Sudan 2,600,000 United Arab

Emirates

120,000

Tunisia 173,000 Yemen 210,000

Upper Volta 6,000 IPS* 200,000

Western

Sahara

92,000 China 600,000

Australia 120,000

Canary

Islands

4,000

Total 12,999,00

0

Total 5,256,000

Grand Total 18,255,000

* Independent States of the Soviet Union

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Table 4: Estimated population of South American camelids

Country Llamas Alpacas Guanacos Vicuñas

Argentina 75,000 2,000 550,000 23,000

Bolivia 2,500,000 300,000 ? 12,000

Chile 85,000 5,000 20,000 28,000

Peru 900,000 3,020,000 1,400 98,000

Australia < 5,000 > 5,000 A few in zoos 0

Canada > 6,000 > 2,000 < 100 in zoos > 10

Europe < 2,000 < 1,000 < 100 in zoos < 100 in

zoos

United States > 110,000 > 9,500 145, mostly in

zoos

0

In ISIS

registry in

zoos*

343 303 397 100

Total 3,683,343 3,344,803 572,142 161,210

Grand Total 7,761,498

* ISIS = International Species Inventory System Table 5: FMD in New World Camelids FMD Serology: Field investigations. Reliable serological tests are available So far all investigations are negative despite NWC mixing with FMD positive contact

animals Experimental investigations Antibodies have been produced to FMD using different routes and serotypes FMD Infection: Field investigations

One case in alpacas showing minor disease, but no virus isolated Experimental investigations NWC can be infected with different serotypes and demonstrate mild to severe clinical signs. Virus can also be transmitted to other susceptible animals. FMDV was not isolated after 14 days. No carriers?

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Table 6: Reports on dromedary FMD-antibodies from field surveys Authors Year Country Serotypes Sera

tested Positive %

Test Endemic

Richard 1979 Kenya A,O,SAT1,2 87 2.6 VNT* yes Hedger et al. 1980 Oman A,O,C,SAT1,Asia1 203 nil VNT yes Moussa et al. 1986a Egypt O 1755 5.4 VNT yes Paling et al. 1979 Nigeria C,O,SAT2 88 nil VNT yes O 536 nil AGID** Abou-Zaid 1991 Egypt O 536 10.6 ICFT*** O 536 23.5 ELISA

yes

Hafez et al. 1993 Egypt O 364 nil VNT yes Hafez et al. 1993 Saudi

Arabia O 650 nil VNT yes

Moussa+Youssef 1998 Egypt O 169 24.3 ELISA yes Farag et al. 1998 Saudi

Arabia A,O 25 nil VNT,

AGID yes

Wernery pers. comm.

2003 U.A.E. O 374 nil ELISA yes

Younan pers. comm.

2003 Kenya O 324 nil ELISA yes

* Virus Neutralisation Test ** Agargel Immunodiffusion Test *** Indirect Complement Fixation Test Table 7: Seroconversion in dromedaries after inoculation with FMDV

Author Year Country Dromedaries tested

Serotype Inoculation Route

Method Result Duration of antibodies

Moussa et al.

1979 Egypt 5 01/2/72 Egypt

intranasal SNT* AGID

5/5 0/5

nil

Nasser et al.

1980 Egypt 2 01/2/72 Egypt

intransal Not done ?

?

Metwally et al.

1986 Egypt 2 01/2/72 Egypt

intranasal FAT** 2/2 low titres

6 weeks

Moussa 1988 Egypt ? 0 intranasal SNT positive low

3 months

Abou-Zaid

1991 Saudi Arabia

? 01/2/72 Egypt

intranasal ? Nil nil

SNT 3/3 10 weeks 3 01/3/87

Egypt intrader-molingual

ICFT*** 3/3 6 weeks

AGID 0/3 nil Hafez et al.

1993 Egypt ELISA 3/3 11 weeks

SNT 0/1 nil 1 01/3/87

Egypt footpad ICFT 0/1 nil

AGID 0/1 nil ELISA 0/1 6 weeks

* Serum Neutralisation Test ** Fluorescence Antibody Test *** Indirect Complement Fixation Test

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Table 8: Reports on experimental FMD infection and virus isolation from field cases

Authors Year Country Mode of infection

Dromedaries tested

Serotype Clinical signs

Virus re-isolation

Moussa et al.

1979 Egypt Intranasal 5 01/2/72 Egypt

nil 1-4 weeks OPF

Nasser et al.

1980 Egypt Intranasal 2 01/2/72 Egypt

nil 1-6 days faeces

Metwally et al.

1986 Egypt i.v. 2 01/2/72 Egypt

nil 1-3 weeks

Moussa et al.

1986 b

Egypt Intradermolingual 5 01/2/72 Egypt

nil Blood

Hafez et al.

1993 Saudi Arabia

Intranasal ? 01/2/72 Egypt

nil ?

Abou-Zaid

1991

Egypt

Intradermolingual

3

01/2/87 Egypt

yes

Blood, OPF, faeces

Footpad 1 nil Negative Kumar et al.

1983 India Natural 2 0 ? Tongue/gum from one

Moussa et al.

1987 Egypt Natural 4 0 Vesicles ulcers swelling of limbs

Ulcers

Farag et al.

1998 Saudi Arabia

Natural 30 nil nil Probang

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Figure 1: The forestomach system of Tylopoda DGS = dorsal glandular sac; VGS = ventral glandular sac; C1 = compartment 1 (rumen) C2 = compartment 2 (reticulum); C3 = compartment 3 (tubular stomach); DU = duodenum Figure 2: Feet of a llama and a dromedary

DGS

C1C2

C3

VGS

DU

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Figure 3: Mating camels

Figure 4: The rutting bull inflates and exteriorises its “doula”

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Figure 5: A slippery third membrane surrounds the newborn calf

Figure 6: Distribution of C. dromedarius and C. bactrianus

C. dromedarius C. bactrianus

C. dromedarius introduced

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Figure 7: Subepidermolingual FMDV-inoculation of a dromedary

Figure 8: Typical FMD lesions on the tongue of a heifer three days after

subepidermolingual inoculation

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Figure 9: Probang sampling of a dromedary