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HOG CHOLERA IN THE PHILIPPINES
Se\·erino L GATAPlA"'
Hog cholera, the English or Lhe classical swine fever. an acute, highly contagious, viral disease affecting swine of all ages is still considered the most destructive 0f swine dise<1se2 in the Philippines. This disease is endemic in our country.
Historical background It is not known exactly when hog cholera first occurred in the Philippines but evidence shows
that it has existed in our country many years before 1900. The first authentic report of its oc· currence was in the later pan of 1901, when Dr. David G. Moberly, an American Veterinarian found the disease in the province of Bulacan where it had widely spread throughout the province at that time. This report was corroborated by the result of the first investigation made on the disease at Angat, Bulacan in 1903 by Dr. David G. Kretzer who was working at that tinie for the Philippine Government. In this province alone there were reports of 500 hogs c,ying each month. From that year on. the disease has been reported in every province. 6 '
Hog cholera situation Staristics from the year 1934 to 1950 show that the disease incidence has continued to rise year
after year. 1 ' It appears that the number of hog cholera cases has increased with the progress of the swine industry, the mortality from the disease ranging from 70 to 95% (Table 1).
Up to the present, the hog cholera situation has not improved very much as the number of cases either continues to fluctuate at a high level or is still on the rise although with a reduced rate of mortality, in spite of the continued immunization being instituted. This is foe situation depicted from 1964 to 1978 data (Table 2). During this current year (1979) for only a period of 5 months some eleven (11) provinces have already registered more or a little less than the total number of cases in the preceding year (1978) (Table 3).
A more detailed analysis of the disease situation in the country for the period, 1970 - l!:l78, as shown on Tables 4 & 5, revealed the following: In general, in the relatively progressive provinces based on the hog population, i.e., where most of the swine are raised individually or in the backyard, the number of deaths recorded, with a few exceptions, was quite high ranging from 411 to as high as 22,369 swine afflicted, with the number of reported cases being quite high, too (6~{ to 6,935), i.e. a mo1i:ality rate ranging from less than l % to as high as 100% in certain provinces, or an average of 35'1/o.
The number of cases in relation to the swine population of the provinces where pigs are raised in the backyard ranges from less than l % to as high as 58%. The high rate was especially encountered in places with frequent outbreaks.
In the provinces ,vhere the greater part of the swine population is commercially raised, the percentage of those that are affected with hog cholera in relation to the hog population of the province is comparatively much lower (0.7 • 9.2%) than in the case of those raised at the backyard level, but the mortality is still quite high ranging from 2.5% to as high as 81 %, or an average of ?S'Vii also. This may be attributed to the much better preventive measures commercial farms an: instituting, but once the animals become infected the loss is as high as in the case of backyard raising.
Considering, therefore, the number of pigs that suffer from the disease including those that finally die, the loss is really tremendous.
• Supervising Planning Officer, Planning and Management StafL Bureau of Animal bdustry, R Magsaysay Blvd., Manila, The Philippines.
1934
1936 1937
1938 1939 1940
194!
l 945
1946
1947
1948
1949
[950
Year
63 - 64
64 65
65-66
66--67
67-68
68-69
69 -70
70-
"" 72-·73
73 74
74 75
75-- 76
76-- 77
77-78
Year~ nurnber n1onths year. cases and
·---~-- ··-------------·--·------- - --·-- - -·-~-·
JU
3
12
12
40
264
499 , 19
3.233
2.()57
2.3J D
361
248
1,445
2.070
2,915
I .. S98
2.61 l
2.902
4,760
7,832
v:un
Table 2 Hog cholera situation for the fifteen year period,
Number 0f hog cholera
cases
I 0, 3 l
1,527
7,586
9,1 l 7
9l,ll7
17 ,43:
37,902
49,793
59,796
44,949
6,491
90,072
Number of from
hog cholna
6,495
4,131
5J 82
10,726
9.451
9JJ8l
l 1.910
l 3397
l 6.427
9.815
l, 16 7
6,296
Number of hogs vaccin~tcd
J.gainsl HC
96,
I 9 7 ,5 l8 (Lll75 private
included)
555,186
292,076
395,446
451,368
606,181
64 l.338
742,609
1,039,323
849,82(,
1,014,755
925,l l ----·-----·-·-·- -·--·--------·---- --
l2
54
47
8
18
o. 7
"I'he situation depicted above is indeed so true that e;:en at this stage cf th2 df the swine industry in our country, where we claim to have advanced so much rn the techr:nl;,gv oi !';-.,.-inr production, hog cholera is stiii with us. Even at this stage where we have a Wffiety o{ su1fonamide preparations. narrow or broad spectrum antibiotics and all sorts o-:' dr:~i n:icrn~,ial f.'rc;:,arct1 ;rn,••:, including sern and vaccines, it appears that the disease is to stay with 1,
Table 3 Hog cholera situation for !ht' first 5 months of 1979 in a few ,dfcl ·o pruvin:·,.s
llocos Norte
LD Union
Panga:,inan
Bulacan*
Tar lac*
Aurora
Cavite
Laguna
Minde>ro Occidental
.M. Oriental
Pabwan*
Romblon*
Sorsogon*
Aklan*
Cebu*
Sulu
Misamis 0cc.
Davao Oriental*
Davao de! Sm*
Lanao dd Norte*
Antique*
Nun1bcr of hog choJ,;:~ra
Nurnb-.~r of deaths from
cases hog: cholera
8
98
416
·y ,,:,
5
1' ,,
: 4
54
60
l l2
1.730
462
3
306
242
312
91
1
8
35
£~25
5
5
11
2
4
9
25
1.646
39
3 V -'
123
25
14
100
)0:J
36
54
20 JOO
100
JOO
JOO
100
17
22.3
95
8 5
JOO 100
No. of c:t'::_:~; higher UL:n1 1-Jic 1eld
number qf c~l\C\ of UH: ~Hel·eding ye:1r.
do~
No. of cases ?"ur;hcr than the: tc U.il no. of cases er the pr'.x:cding y~ar.
l\io, of ta&er; little less than that in I 978.
No. of c1sc!; 3--i/2 1i1ncs that in 19 78.
No. oi cc.,es 34 li:nes that in ] 978.
NcL of cases a iittJe k:-:-:, t!:~n1 the tolat of l 978,
l (L l 3 No. of c;_:~,• .. ·:-: cAcccdinr 1-he tot:,1.l nG.
of case, in 1918.
51 No. of cases 3~1/2 tj1nes i!1at in !97~:
8 Nn, of ::-:1~-,c~ c_\ccedrng :he tnta1 no. of case;; in 197
!54 l 978.
* The eleven provinces that registered high number of ca,cs.
Table 4 Hog cholera ihuation in some selec~ed p1\J\·inces v:here the g.reater number of hogs are rni~ed in ihe backyard
Provinces
Pangasin,.n~ 9
Cagayan 7
faabela 8
Quezon 9
Albay 9
Can1arines Sur 9
Iloilo 9
Ncgros 0cc. 9
Bohol9
Cebu 9
Negn)s Oriental 9
Nueva Ecij:1 9
LeytG 8
Zan1boang:1 del Norte 6
Zamboanga de! Sur 7
Bukidnon 4
Misamis Or, 9
Batangas 9
Davao de! None 8
Pampanga 9
Tarlac 8
**Palawan 9
**Lanao Norte 8
**Siquijor 6
**lfugao 4
"! of Hog raised in
thE' bkyd.
90 99 81
96
96 97
95 75
99 85
'l8
88 99
98
99.7
78
66 99 66
68
99.8
83
100
99.4
Tot. hog pop. as
of Jan. "78
14.5[()
315'.,E88
207 .650
189.400
\08,440
200,340
147.050
145,330
2:10,680
118.2'.H)
147,500
.l. 08,_600
j !.7
125.810
151,070
142,370
171 .400
150,240
l 10,92U
139,64()
l i 8,520
50,970
54,lJO
35,670
34,990
* Selection based on hog population
----, --~- ---·----- - -----·- -
rot. no. of HC case~
2,898
4,051
4,345
3,939
411
22)69
l ll,994
7,840
f.,S89
! 7,275
5.658
i 8.001
l .l 25
l ,908
499 4,454
5 i ,688
3,058
22.061
18,67i
29,621
966
25
335
Tot. no. deaths fr.HC
l,410
2.lJ73
2.691'.
2,827
63
2.564
6.935
:i.212
3.Sl 8
i.173
1,231
3.02]
942
61. J
473
300
I ,(163
2.762
392
1,005
1,099
7,033
336 20
247
Mortality ran7e in
29 l l
22
67
87
44 -- 89
4'.'
8 83
l3 62
6 83
9 · 98
3.4 ~- 77
5
2
15
20
l.'
5 l
l l
0.2
2.5
2
2
18
6
60
33
41
95
39
9 ., ,.
65 JOO
49
66
79
8
- 100
85
88
- 100
100
Numbers following the name of the provinces indicate the number of years data were collected; period covered, 1970 - 1978.
** Provinces that registered quite high number of cases or high mortality rate
J'ahle 5 Hog cholera situation in provinces where more hogs are commercially raised
Provinces of Hugs
raised
con1rnerciaU:/
Total lwg population as of Jan.,1978
rota1 no. of HC cases
Tot.11 no.
deaths fr.BC
Mortality range
Ave1:igc mortality
49
62
72 !5
46
3 l
16
47
lR
7
53
5.2
54
25
60
24
5 3
) 3
5
6
24
35
80
74
Average mortality
---------~-- ----
Bulacan 9
Laguna 9
Rizal 9
South Cotabato 7
-----·---~--
77 288.4 l 0
57 99.070
74 161.250
77 240,940
1,913
9,160
10,967
3.223
861 l', - 61
5,654 8 ·~· 81
1,763 2.5 - 60
s~~ .<., ~) 4 52
Numbers following the name of ihc pro,'inccs indicate the number of years data were collected; period covered, 1970 ·- 1978.
45
62
16
18
15'.7
Mode of transmission or tlis~emimnion oi hog ,:lmlera Hog cholern iS rnmsrnitL,,d principally by ,mimc::te u)r,tact with ;:.;;:k animals and direc;]v cir
indirectly with flesh ;,eiT:rtr-:·;" J.nd excretions U·,c,t .·,,nt:-im rhe sphen,:::, l<.'•i) virus. In the early days \·vhen hogs were allowed run Ht largt:'. and forage for theP1selves~ they c:an1e
in contact with sick pigs and acq,,ired Uw inlection chis way. Tb:: other means d1 e: the selling uf slaughtered pigs without veterinarv inspection: the clandesti:,e slaughter and pedcti:ng of pork. feeding of pork trimmings. scraps and wac;hings from infecte·d slaughtered 211imals; aliowing movement of oigs from province rn •.cithout veterinary h;:a.lth certificate or permit: and the sale of the newly immunized swine vaccimned hy the simultc1,1eous serum--virus rr:etnod or the indiscriminate use of the virus and serum for the inununizat i,Jn. ')
At present, the sale of slaughtered pigs without vete•inary ins;:iec-tirm is completely banned although there may still be a few secrete slaughters and s11les of pork. Tbicc;, nf course, is not much ot a problem now. Pigs are now generally raised n:. uyr;me rne,,1. or pem. sv that dissemination of tbe disease through this way has been partly preYentt:,L lfov:ew;, the n;1_,,;,,1nent of swine which rnav be in subclinical cn,1ditinn :)r have been exposed to infectic-r, and ma, h,· in the incubation p•cric,(! still continues. Sometimes piglets are Deddled from place to place tc those who raise one or lwo pigs in their backyards." At times, the int,oductwn of an animal into the herd without previously under· going quarantine has been incriminated. The movement of people, from infected places or herd to another. especially hog dealers has alsl• b(cen incriminated. Birds and rats were also ,;usnected in certain outbreaks.
The feeding of i;;arbage or kitchen "'craps is still practiced especiallv hy the backyard raisers. Even semi-commercial piggeries feed their anip;,ils wi; h kiti. bt·n scra;1:1 ur le Hovers from hotels and restaurants, but the possibility of transmission through ,his means has been greatly reduced by first cooking this kind of fe.-.•d. Since swine lungworm bas beeri demonstrated tc act as reservoir and intermediate host of the hog cholerd vims, and since swine lungworrn iufoction is common in the Philippines. the possibility of soreading the intection this way may nm !"Je '!"rnde.
Manifestations of hog cholera During the early years of 1900, v,rhen the disease was first rc:·ported and investigated, the acute
fonn was mostly encountered. especially in the slaughterhouses and hog corrals in Manila."' As this form of hog cholera nms a rapid course, cases of this disease were rarely dia1snosed in life dt that time. The first few signs of the disease are indifference of animals to their surroundings. An af• fected animal may or may not lose appetite and in some cases may even eat until a few minutPs before death. Usually they c:tay quietly in a corner or may crowd together and force themselves taking refuge under litter., Death in the acute foim generally comes in a few hours and rarely does an animal with this form liVt, more than a day or two. They refuse ,o rnnve when disturbed a.nd appear unmindful of their suffering.
Constipation is ordinarily observed in the beginning and is then followed by diarrhea up to the time the animal dies or up to the time that it recovers. Sick pigs register temperatures ranging from 101 ·· 104 ° F and have difficulty in breathing. There is reddish or bluish discoloration of the skin around the nose (snout), ears and abdomen and inner surface of the thigh. The conjunctiva is generally reddened and a mucopurukcnt discharge from the eyes is frequently seen. The nervous symptoms are manifested by local paralysis, incoordination of movement and occasional sluggishness and at times convulsions.
Diagnosis During the June 25. 1933 hog cholera outbreak in a local farm which killed some 76 swine,
consisting of ~ucklings, sows and boars, veterinarians found difficulty in diagnosing the disease. It was only after autopsies were conducted in August 19:14 and definite lesions of hog cholera were found that the outbreak was declared. 51
Knowing that prompt diagnosis is extremt,ly important as delays in diagnosis will often result
1'18
in the lc,ss of the entire herd, in eai;e of doubt, the disease is tn:-aied as hog cholera llnt:: prm·e1~ otherwise The presencE' of hemorrhages in the larynx, kidneys and bladder and th:: button ulcercaear the ileo-caecal valve are strong indications of hog cholera.
The discovery of the presence of swine erysipelas in the country, especially the acme type: uf infecr:ion has often caused serious difficulties in the diagnosis of the acute form of hog cholera. Fluorescent antibody method which is the preferred method with diagnostic laboratories for the detection of hog cholera v:rus is not yet employed in the country. although there are already experiments along the line.
Most of the cases of hog cholera are diagnosed clinically in the field based cm the history. symptoms and lesions. Confirmation of suspected cases of hog cholera is done in the central diagnostic laboratory of the Philippines Bureau of Animal Industry by autopsy, histopathoiogy and sometimes by animal inoculation. The specimens often submitted for the diagnosis are dead or sick piglets, viscera or head.
Prevention and control Since the discovery of hog cholera up to 1928, practically little has been done toward its control
and eradication.') During those years less attention was given to this disease because of the ravage of rinderpest at that time. The only method of handling the infection then was the institution of sanitary measures such as disinfection and quarantine. Hogs clinically positive were isolated and infected pens were cleaned and disinfected. Pens were disinfected with creolin, lysol or crude carbolic acid solution. Infected and exposed animals were disinfected with mild solution of the same disinfectants_
It was in the early part of 1928, when infected and exposed pigs were actually treated. The serum alone and the simultaneous serum-virus treatment which were the methods developed and widely used in the United States were adopted by our country on a small scale. The technique is as follows: (l) Animals' temperature is taken and those found with fever are given serum alone; (2) Animals which are apparently normal receive simultaneous serum and virus injections.
The larger portion of serum used then was imported from the United States and a limited amount was produced by the Philippine Bureau of Animal Industry Research Laboratory (PBAIRL). The virus was completely supplied by the PBAIRL. The amount of biologics utilized was negligible in relation to the population of swine (Table 6).
This treatment was instituted by the Bureau's veterinarians or their authorized representatives and never entrusted to the private sector.
This was the method employed that freed Alabang Stock Farm, a Government Farm, of hog cholera.
In 1939, the hog cholera vaccine-crystal violet vaccine and tissue vaccine-came into use. With limited amount of vaccine available-partly imported and partly locally manufacturedimmunization went on non-exposed animals and herds. With very insignificant amount of biologics used at that time the mortality from hog cholera was tremendous. For instance, in 1948, the reported 7,642 cases resulted in 5,611 deaths and in 1950, among the 7,554 cases, the deaths numbered 6,434 (Table 1).
During the campaign in those years for the prevention and control of hog cholera, the BAI personnel were guided by the following: (1) The use of attenuated vaccine in towns or municipalities where pigs are raised individually and
where they are turned loose to forage for themselves; this method is also employed for offsprings intended for stock which are confined for at least a week after immunization before being turned loose again. Animals exhibiting severe reactions are to be given serum and confined for further observation. Offsprings from non-immunized sows which are intended for the market are to be immunized with crystal violet blood vaccine or tissue vaccine soon after weaning and revaccinated after 3 months, while those of immune dams are vaccinated a month
Yea;-
1929
1930
1931
J932
'.933
.934
193.'>
1936
193 7
1918
l.939
1940
1941
194 2
1943
!944
1945
l 946
1947
1948
1949
Table 6 I\.mount of biojngics use,! in. relation to the s,vine population
!i();: <:'1'.J]Cra
vinh jn doses
L638
1 J)60
2,61 !
4.760
375 2,8511
2,375
6.0 79
12.494
10,263
12,684
H-,~ choler,, senun ;n cc
·7 01.C I•/.__,,.)
2,795
6,43 1)
2='. 600
i6!i10
l2,00U
J0.300
4U.J.50
l 7 l .500
362 _:,{;0
Hog chokr;a1 vai..:..:int: )n dchC\
5.705
i 2,150
l l.100
1 LI 70
Sv1,:inc popu1dtion
2,491,245
2.594,620
2,88fUJ29
3.1118.758
3J. 20,22~!
3. ! 83,()39
3 . .558 .. 274
3,348,515
4,446,190
l.983, 720
l.460,78()
i ,7'i2.9J3
2,636.820
3.448,86'
or so after weaning and revacdnated also after 3 months. These immunized pigs are confined for 2 to 3 weeks after vaccination. Stock and rnarket pigG Zcre to be hous .. ,t1 separately.
(2) In organized piggeries where the original stock are im.munized by any standard method or are not immunized at ail, either blood or fo-sue vaccine is to be ust:d for all offsprings.
(3) Inter-provincial and inter-island traffic of swine must be regulated with permits for shipmer:t being issued only to healthy swine and those which come only from places free of infection.
(4) There should be strict enforcement of the meat inspection reguiarion. (5) During the information campaign, one should promote the importance of swine hygiene and
sanitation, methods of disposal of dead and sick animals and of their discharges and secretions, effective method of disinfection and prompt reporting of the presence of the disease. Some problems met during those years in the control of hog cholera in the Philippines were the
following: (1) Non-availability of an ideal vaccine--a vaccine that is cheap, safe and potem; one that would
confer life long immunity with a single injection, and which is not eliminated or, if eliminated by inoculated ho).(, has no power to infect non-vaccinated susceptible swine.
(2) The custom of allowing pigs to roam (3) There were some deaths occurring during the use of the simultaneous serum-virus treatment.
At present, the serum alone treatment is still used in the prevention and conrrol of hog cholera. The hyperimmune anti-hog serum is used especially fnr exposed susceptible pigs to provide immediate prot@ction. Jt is eifective but is expensive and the immunity afforded is of short duration. The serum trearment is also being resorted to for the therapy of hog cholera, but likewise. the animal dies once symptoms of the di:>ease become apparent.
t60
it,, ll.te sin:u.J. :aneous seru1n-vin.2s treatrHe.nt J: ~Jr imrnunizing s\v'ine
c wo 1 v1.:es of modified vaccine are in use. dtolera vaccine. chr)lera 11a.ccine is
presently being- produced by the Phihppine I1ureau of 1\nin1.(1J forrns p:1rt of the t:ota1 an10unt of vaccinf: u.~·:.ed nnrnunizing our swint~ 1 ... his tyDt'' va.ccine is used by our fo,·ldmen in the vau:i1.2.ti:;r: ,,t·,,gram. The voltLtK produccz1 0ur Bureau of Anirr.:,1 lndustry can had],, JI,"<", :}1e demand for om ir.:F, ,,:.,iz?i'il:1 pro1< can.: Lble 7) The va,:c:nt' produced_, at least~ anr;\vers for about .20°;0 of t.hf tot~}} dernand .. T'he re~;t of the hog cholera vaccine ,equirement is supp!ied b,· in11,c,nation.
The atrenuated tissue cullure ·:accim: is ienJorted irom cou,,::i ics producing· it. £•·om the U,1i,ecl States. This type of vaccine is fh: or,c oimally used by the p:·ivate sector,
1~·he serurn is also being used b;r· othe,r:~ in cases \vhere. se\.·erc reactions to ·\:-ac( in.at.ion ,vith either tlie !apirn1:ed or the attenuau,·d :is.,:u,· ,:t;nure vaccine take
Researches on hog cJ10le1·a A few studies have bee,, conducted on hog c.1101era At the tirne ,,1;/f1en the siinnltaneous seru1n~virus rnethocI cl i1nmunizing pigs against hog cholera
was employed, aW.'mp~s were made to adapt anti prcpag;ire ,'·!e virm; 1r1 rabbits by serial passag.:.-:, ,vhich failed. 21 The 01her trials with the same ,vu,,. serie,, c,f ratbi.t to rabbit passage·, asing this time diiferent passage levels of the alternately ,Ja,,.,,ed vims. /\Jrh()ugh the prnces~, 1s a v1;1y :;]ow 0;1e. it was found possible to ;;,rbpt crnd propagate the cholera virus in rabbits.
Resea:-cries were l;,ter directed imv producing a vaccine'. Ti1i'.• v. as at the tm,, ,vb,n the ciystal violet vaccine, ,m inactivated virus JJ!·epara1io11 was in use. We found the inactiv::ited ,:rvstal violet vac,;ine not so appropriate for usf• in the Philipvines where hog d111lera is enderni,.:. as rhis vaccine confers effectiv·e imn1unity on the lLlth to :?. 1st day after inoculation (rneaning too slo\v) and the protection afforded lasts for only 6 mom}1s ic 1.2 months at mot.t. 1'he modified live vims vaccine v,as found more apprnmiate for rhe Philippine cm:d:ti,Jn3 S'! Lhit;_ experimer:1.s toward producing this
Table 7 Amount nf heg chokra vaccine produced in rc,h1!'-l)n to the nurr1h<2r of animals va<:'cinated
========::cc:============----· ---- ----- -------·
Year
1964 -65
1965-66
1966--67
1967-68
1968--69
l 969· 70
1970-71
[971-72
1972 73
1973 .. 74
1974- 7.'i
1975 76
1976-77
1977 78
1978 -79
Hog cholera vaccine manu
factured (in doses)
26,l 75
41.100
272.920
787 .6011
393, i 26
308,041
680,420
484,650
700,000
227.001)
163.630
Hog cholera va,.::cin~ dispensed
for disea,e control
20.0~~5
23,81:J
252,530
263,5lH)
390.1 I 6
Hog cholera V<1ccim. sold
1. ,{)75
35
3,400
3,560
3.tllO
-=====·-- -------- _,, No, of :1nirnols
vaccinated against hog cholera
555,l 86
292.076
395.446
451368
641,338
i .039, 123
81.19,826
] .014 .. 755
925.1 l 2
l<ind n:i v,;ccine w,·re unoert,iKen. Ar:'.sptatio:· ,F,d atren;,,tlion o;' the iw)<; cholerrt -.·irus b> ,':e altenl.ilt;ro{ tech_nfr.rue in rabbit;:; was sta.rted. 31 "1'lds gave .,variable results bec?use of the tendency of 1!1<: virus to gei' lost or die during ,nc proce""·
The 20th passage m rabbit failed aln::a(,y to info::t, but titc, f.1roduct has a 10,v keepmg quality when stored. In potency trials conducted at th1'-' passage le\·e:l some anir,1,ds are already protected out such degret· <•f attenuatint cannoi. yet be 'T:..nmrne11c:,"; Based on 'tlf'Se findrngs it wa;; conduded that not all rabbits are smtable passage animah; ,:ertain animals are susc~,ptible while other:< are resistant
In another study•) with the same objectivecc of ilttenuatir:g the hog cholera virus, the alternating passage of the virus through pigs and duck embryrmated eggs was employed in two batches of emb1-yonated eggs. The intravenous route of ii10culation was used in om" batch and the allamoic sac in the other. The attempt failed to attain the desired results. From the limited data obtained from the study it was tentativeiy concluded: that duck embryrmated egg trnly attenuates, but to the extent that it completely denaturized the hog cholera vims; that the duck embryonated egg is not a suitable medium for adaptation and/or attenuation of the virus.
The immunity afforded by the lapinized vaccine lasts for 8 to 12 months and failures in vaccination happened because of low keeping quality and may be by improper handling.
There were also some failures reported on the use of imported vaccines and these, too, have been ascribed to improper handling or improper storage during shipment. Hence, researches are geared towards improving the hog choiera vaccine. To produce the tissue culture hog cholera vaccine is one study now being conducted
As the production of the lapinized vaccine is now getting too expensive due to the rising cost of rabbits, the development and production of a tissue culture hog cholera vaccine that can match in quality the imported preparation and which can be produced in our country economically and in sufficient quantity is considered a very timely undertaking.
There are also researches to improve our methods of diagnosing hog cholera. There are already trials employing the fluorescent antibrxly technique, a technique which is already in use in foreign laboratories. These researches aim t1, make acrnrate and faster the diagnosis of hog cholera.
References 1) CORONEL, A. B. (1950): The stat.us of hog crwlera in the Philippines. Philipp.] A nim. Ind 11,
(2~4) 75-82, 2) _____ , (1950): Preliminary report on the propagati@ of hog cholera virus in rabbits.
PhilijJJ)./ Anim. Ind. 11 (2-4), 107-111. 3) ·----, <1950): Progress report on the adaptation and/or attenuation of hog cholera virus
by the alternating technique. Philipp. J. A mm. Ind, 11 (2-4). 139-157. 4) --··-----, and ALBIS, F.S.: Preliminary report on the attenuation of hog cholera virus by
alternating passages through pigs and duck embryonated egg. Philipp.}. Anim. Ind. 11 (2-4), 127-137.
5) FARINAS, E.C. (1935): Hog Cholera-Its control or eradication in the Philippines. Philipp. ]. Anim. Ind. 2 (5), 333-343.
6) MOBERLY, D,G. (1908): Hog cholera, Philipp. Agric. Re,;. 1 (2), 91-94.
Discussion Kumagai, T. (Japan): What is the cause of the variability in the mortality rate of infected
pigs among affected areas;, Answer: The variability in mortality rate can be explained by the fact that commercial farms
are following a strict vaccination program whereas the backyard raisers at times do not vaccinate at all because of unavailability of vaccines. The virulence of hog cholera (HC) strains may be mentioned but no studies have bccen conducted along that line, yPt.
Koh, J.G.W. (Singapore): L Is there any difference in the susceptibility of indigenous breeds
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;:,f pigs and commerci<1] :)1\::ed'., in the Phiiippinr:.0.:· 2 1,, there any ,;;::ietence in the virulence Gf 'iarious isolates of hog cl,o\,,n-1 v;ms in the Phi!ippinps':'
Answer: 1. W r do nc/ ~ee any difference in E;:,s,:cptibilitv of the iedigenous breeds of pig<: ,md ,.·:nmnercial breed1: :,:c !nng as they are not vaccinated or p:-c_,vi,msly exposed to the infection. 2. A,: far as the viru!e!1ce of various iso!,1tu, ,,t hog cholera (BC) Yirus rs cnncerned, we have JliSt started a study in this reg·ard.
Shimizu, :VI. (Japan) Comment: I ViOulci like to make a fe,v c,nnments on the viruience of HC virus. We have ubtained several isolme~; in pathogenicity from field case~, 0£ hog cholera. The relationship between the antigenicity ;md the virulence was investigated in these fr,olates. Eleven strains were examined for the degree of neutralization by antibodies against bovine viral diarrhea lfstP) vims which is antigenically related to IIC vimc;. The HC virus strains were divided into two groups: J. a group showing weak neutraliz;iJion by BVD antibodies. 2. a group with marked neutralization depending on the kind of BVD vims strains used. The findings suggest the existence of variability in antigenicity in both HC and BVD viruses. The pathogenicity of the strains was also investigated. When HC vims strains which were neutralized ·weakly by BVD antibodies were inoculated to pigs, they gave rise to severe symptoms (acute form) whereas those well neutralized by the BVD antibodies had a low pathogenicity (subacute and chronic forms, inapparent infection). The clinical and immunological response of pigs inoculated with Kanagawa/7 4 strain (the representative strain of the second group) enabled to divide the pigs into four categories. 1. These pigs developed a subacute form and showed a severe response 2-3 weeks after the inocuiation. 2. These pigs showed severe symptoms and even died 14 weeks after inoculation. Virus was recovered from the serum and the tissues. In both cases 1 and 2 the titers of serum neutralizini antibodies were low. 3. These pigs showed mild signs and recovered 4 weeks after inoculation. the vims could be isolated from the serum at the eariy stage of infection. 4. These pigs showed no clinical response. Both 3 aPd 4 categories were rare and in these cases the antibody titers were high. It thus appears from these studies that the antigenic properties•of HC virus are related to the pathogenicity in pigs.
