Screening of Domestic Ruminants Sera for the Presence of Anti-camel pox Virus Neutralizing Antibodies at Al-Hassa District of Saudi Arabia

Department of Clinical Studies, College of Veterinary Medicine

King Faisal University, P.O. Box 55011, Al-Hasa 31982

Screening of Domestic Ruminants Sera for the Presence of Anti-camel pox Virus Neutralizing Antibodies at Al-Hassa District of Saudi Arabia

(With 2 Tables and 1 Figure)

By

Fadhel M.T. Housawi

فحص أمصال المجترات  المستأنسة لوجود مضادات الأجسام المناعية ضد جدري الجمال بمنطقة الأحساء بالمملکة العربية السعودية

في هذه الدراسة تم فحص مجموعة أمصال الحيوانات المجترة المستأنسة وذلک لمعرفة وجود مضادات الأجسام المناعية ضد فيروس جدري الجمال . وشملت الدراسة أمصال کل من الجمال ، الأبقار ، الضأن  والمعز جمعت من الحيوانات الموجودة بمنطقة الأحساء بالمملکة العربية السعودية.

هذا وقد بينت التحاليل عن وجود ما نسبته 21% للأجسام المضادة للجدري في أمصال الجمال المرباة بالرعي البدوي ، وما نسبته 4 % فقط في أمصال الجمال التي جمعت من المسالخ ، بينما لم تسفر نتائج التحليل عن وجود أي من الأجسام المناعية المضادة في أمصال الأبقار، بينما وجدت ما نسبته 4 % ، 10% في أمصال کل من الضأن والمعز.

هذا وقد تمت مناقشة نتائج دراسة الأجسام المضادة في الحيوانات المذکورة أعلاه وعلاقتها بوبائية مرض جدري الجمال في المملکة العربية السعودية.

SUMMARY

          Examination of ruminants sera for the presence of anti-camel pox virus neutralizing antibodies in Al-Hassa district has revealed that, the prevalence in the nomadic pastorates camels was 21%, while in abattoir camels' sera 4%.  Bovine, ovine and caprine sera have produced zero, 6 and 10% prevalence.  The presence of such neutralizing antibodies in the animal sera was discussed in relation to the epidemiology of the disease in the country.

Key Words:  (Camelus dromedarius), anti-camel pox virus antibodies,

                      Al-Hassa, KSA. 

INTRODUCTION

Camel pox is an infectious disease of camels, manifested by cutaneous nodules on the skin (Rash lesions) that cover the mouth, head, neck, legs and perineal area, or generalized lesions that cover all the body of both Camelus dromedarius or Camelus bactrianus camels. The disease was reported from all  camel raising areas, except Australia (Wernery and Kaaden, 1994). 

The causative virus belongs to the genus orthopoxvirus. Camel pox virus isolates from Africa, the Middle East and Russian were found to be characteristically similar (Davies et al., 1985).

Since the first isolation and identification of the camel pox (CP) in Saudi Arabia (Hafez et al., 1986), several forms of the disease were noted. These included a mild form, slow spreading form and also a severe devastating form of the disease (Hassanein et al., 1993; Alhendi et al., 1994; Abu Elzein et al., 1999; Hussein and Al-Mufarrej, 1999).  The disease has also been reported in some of the neighboring countries such as Iran (Baxby, 1972), Iraq (Al-Falluji et al., 1979), Yemen (Odend'Hal, 1983), United Arab Emirates (Kaaden et al., 1992) and Bahrain (Higgins et al., 1992).

Thorough investigations regarding the prevalence and in-depth epidemiological studies of the disease are yet to be accomplished.

The present work examines the possible presence of anti-camel pox neutralizing antibodies, in other domestic ruminants.

MATERIALS AND METHODS

1.  Serum Samples: 

          A total of 350 serum samples were collected from domestic ruminants. Two hundred were from camels, 50 were from cattle and 100 from sheep and goats.  The samples were then stored at -20^oC.

2.  The Reference camel pox virus:

          A reference tissue culture adapted camel pox virus (Jouf strain), previously isolated and identified (Hafez et al., 1992) was kindly provided by Dr. Habib Al-Khalf, vaccine research centre.  The virus was twicely propagated on vero cells and titrated before its use in the serum neutralization test (SNT).

3.  The Microserum Neutralization Test (SNT):

          The micro SNT, was used as described by Davies et al., (1985), with the modification that, the test sera were diluted in (MEM) medium, without serum. Series of duplicate two fold dilution were made for each tested serum starting from 1/10.  The diluted serum was added to an equal volume of predetermined camel pox virus, containing 100 TCID/50 to each well.  The mixture was incubated at 37^oC for 1h and then overnight at 4^oC.  A 0.05 ml of suspended vero cell culture was added to each well at concentration of 10⁶/ml, prepared in 2% fetal calf serum (FCS) maintenance medium.  The plates were incubated at 37^oC for 3-5 days.

RESULTS AND DISCUSSION

          Results of the SNT (Tables 1 & 2) revealed presence of neutralizing anti camel pox antibodies in ruminants at Al-Hassa district (Fig 1).  Of the total serum samples studied, 33 were found positive (9.14%).  When the  serum samples were grouped according to their species and type of management, it was found that the prevalence in nomadic camels was 21%, and in abbatoir camels it was 4% camels. It must be mentioned that camel pox vaccination is not practiced, so far, by the official authority of the Ministry of Agriculture in this region (Dr. Yousuf, personal communication). This shows that the seroconversion in these camels was due to previous exposure to camelpox virus.

                  Sheep and goats produced 6% and 10% prevalence respectively, and the prevalence in cattle was 0% (Table 2).  In this country, Sheep & goats are usually reared in close contact with camels, so their exposure to the camelpox virus cannot be ruled out.

           Earlier studies by Davies and Otema, (1981) did not reveal cross-relationship between strains of capripox virus and camel pox viruses.  However, anti-camel pox neutralization antibodies were detected in the sheep and goats serum of the present study.

          Cattle produced 0% prevalence. That could probably be due to fact that  cattle are raised in closed farms and this is the typical management system of raising cattle in Saudi Arabia. They usually don't come in contact with any other animal species.

          Because, there is only little information is available about the epidemiology of camel pox in Saudi Arabia,  a nation-wide study is required to investigate the exact prevalence of the disease among camels and to verify the response of other ruminants which share grazing areas with camels.

Table 1: End - point titres of neutralizing antibodies of ruminants' sera     

                 against camel pox virus.

   The end-point titer was taken when 50 percent or more of the cytopathic

   effects of the camel pox virus was suppressed, as the reciprocal of the

   dilution (Davies et al., 1985).

Table 2:  Number of positive serum samples tested against camelpox Virus.

Acknowledgement:

The author would like to thank Prof. ELTayb Abu ELZein for valuable comments, and Mr.  A. Khars for technical assistance.

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Fig. (1):  Location where camel pox were reported in and around the Arabian

               Peninsula.