WE- ETIOLOGY & EPDEWOLOGY

Venezuelan Equine &cephdomyeIitis (VEE) -A Brief Review and Overview Equine Colic -A Brief Rwiew Equine Parasite Control -A Brief Review

Dr. BobBeede is aveterina~practitionerhMe~dim, Idaho,USA. Heis a l onghe member of the Board af Directors of Christian Vebrinsuy Mission,

There are three vira1 encephalitis dimes oommody mierred to as "sleeping sickness" 'that produce cenml nervous system dysfunction in Equine. These similar dj-e syndromes we Eastern Equine Encephalomyelitis PEE) a d Westm Equine Enoephdmyeliti~ (WEE) and Venezuelan wine Enmphalsmyelitis (WEE).

This discussion will be limited to VEE which is a sorne;times fatal nmuIogi- cal ckisease having occurred in borsm and mao in northern regions of South America for nearly 60 y m ,

In 197 1 A n i d md h m we-s of VEE w m diagnosed in Texas-USA. hi* sive vocwr control pmgfms, large regional quwdntines ;tnd muItiple state equine vacch'ittiosi h fhe southern tiem of states kept the outbreak confmd to parts of Texas. VEE has not been diagnosed h the United States since 19'71.

In 1993 d 1996 there were substantial outbreaks in the south of Mexico. In 1 995 folIbin$ Wmnbi81 dsS and flooding, an out break o~~ h Venezuela and northern Celmbia. It hvolved appraxhately 13,000 hutnan mes and an undeter- mined number of equine dearhs.

Theie have b&n no repom cases in Mexico in aver a y w .

The nxmoir far the VEE virus is thought to be wild bir& and rodents. The disease is transmiW by r n q u i ~ e s and other blood suchg insects. Hones are the most important m p l i E e ~ uf epidemic VEE because they prodw1: a virerPlia (high W m d lemh af -3 s&c;ient tu irufkct mqitrjes . TbEE can hen easily h trims- mitted to ather horses by moquitaa and other biaod sucking insects. f i e hedisease may also spread between horses and man by contact w amsol since it is eancenti-akd in ththe>i&vary glads. WE'k more w m o a in p P ~ &an in st&ld horses and is c ~ ~ ~ c m k i t e d in m a s having the appropriate c o r n ~ 0 1 1 ofmewoir hosts and mos- quitoes. The must recent outbreak wed in areas of flooding W e b cmtaine4 a suswptiie population of' horses, b u m , md mules Ixking -a VEE v a d - tions,

IP brsw, clhiml signs occur approximately five dap a$& infmdon and may include fawq impkd v i s i o ~ b g u l a gait, wwdaiug, r- reflexes, h i i n &

VEE- TREATMENT

VEE- Pwm-ram.

I W NEWSLE- VOL. 3 - 9/97 P A ~ E 2

EQUME COLIC

hanging lower lip, inability to swallow and headpressing. The disease can progress. with the inability to rise, paralysis, convulsions, and death in two to three days. Mildly affected animals may slowly recover in a few weeks but may be left with residual brain dzunagc, Mmality (death) for horses with VEE can reacb 50-75%.

Differential diagnosis to consider are hepataencephalopthy (livebrain disor- der), rabies, protozoal myeloencephalitis (EPM), a protozoal pamite brain disorder), verminous encephalitis {parasite migration in the brain), leukoencqhalomalacia (toxic fungal lesion in the brain often from ingesting moldy cam), and EEE, WEE (other viral mccphalitis diseases). All of these conditions exist in weas where VEE is known to OCCUf

There are no specific anti-viral drugs available. Supportive treatment includ- ing anti-inflammatory drugs (phenylbutazone). seizure control with sedatives, and intensive nursing care may be helpful in mild cases. a slow IV administration of high quality 99% DMSO mixed at the rate of I cc per kg of body weight in a IWO soIution of normal saline and given daily for three days may be helpful to decrease edema in the brain tissues. Prevention of body sores and subsequent insect attacks with mum- bent animals is very important in humid cIimates. Even with treatment, mortality can be 50-75%.

Prevention is the best and most cost effective method of control in any disease problem. Since VEE is spread by mosquitoes, mosquito control measures are very ht1pful. This can include drainage of standing water, insecticide treatment of mos- quito breeding areas, and insect repellent use on horses. Removing horses h m pas- ture and stabling them is advisabia during outbreaks.

However in some climates and conditions, mosquito control may be next to impossible, Vaccines are therefore the most effeetivc method of prevention. Horses, mules, and bhms should be vaccinated one month prior to the mosquito season. If the season lasts most of the year, the vaccine should be repeated evay six months. A new vaccine (TC-83) for humans is currently being tested and given to individuats at risk of repeated exposure in the laboratory and the field.

Suspicious equine and human cases should be reported to Government Ani- mal Health-Regulatory Oficials. The earlier an outbreak is recognized the better lhc chance of containing it and limiting losses.

Quarantine of infected animals and the m a where VEE is occurring are oflett of p t value in controlling an outbreak

InJwmutim obtined~?-em: Florida Yeierlt~uy Scene Yol. 6 No. 3. 1997; jm the C~rnplrin NW.F June, I966 published by IICA;Jm#fi VEE Fact Sheet Sw. 1993, USDA A PHIS Verminuy SPtvIm: Dr nm Kordes* Equine D4-e St@ UDA. A PHlS Veterinary Services. &atfsvllle. MD - Pcmm~ai C~mmunkatim: and Dr Vend-ve Ree~c Ctemsm~ Uniwrsiv. Elgin SCfor Resouwe Material.

Colic - A Brief Review Equine colic is a broad term used to describe any pain from the abdomen of

the horse, muIe or burro. The primary cause of this pain is due to distention of the bowel or stomach by the accumulation of gas, fluid, or f d . The accumulation prob-

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tem may be due to obstruction of the bowei or lack of gut motility which moves material through the GI (gastrointestinal) tract. Colic can range from a simple indi- gestion and gas accumulation to complete obstruction, tonion, or death of a segment of the tract with resultant death of the equine unless surgery is performed. Diseases of other organs can cause similar signs, e.g. urethral obstruction, peritonitis, hepalifis, lactation and azoturia.

Colic has many causes. The most common cause is parasites and the dmage they produce (verminous colic). Pamites cause damage by irritating the gut lining, by migration through the intestinal walls and by damaging the arterial walls thus in- terfering with blood supply to tk intestines. Other causes include dietary indiscre- tions resulting in gas atxumulatiofi (intestinal fermentation and flatulent colic); ob- structions or impactions of fwd or foreign bodies; abscesses; intestinal dislocations (torsion, intussusception, vovulus); and tnteri t is.

Most colics are associated with poor management. Lack of dewarming with resultant gut damage; impactions resulting f?om poor dental care or indigestible rough- ages; enteritis from sudden changes in f e d , irregular feeding or excessively rich feeds; sand colics from feeding off sandy surfaces; and spasmodic colic resulting hrn cold water ingestion before a hot equine cools off following work.

Di scamfort of ~ r y i n g severity Stretching, yawning, biting at side Lying in dorsal recumbency

+ Pawing the ground, sawhorse stance Roiling, Thrashing Decrease gut sounds in each flank Elevated heart rate Decreased capillary refill time Pale, blue, or intense red gums Sweating

History of poor management Symptoms o f discomfort Lack o f gut motility Rectal exam - gas or torsion of bowel Ventral mid-line abdominocentesis of peritoneal fluid, should be clear ye1 low if normal Sand colics can be deteclsd by faes examination and hearing sand move- ment upon auscultation of the ventral abdomen

The course of treatment is dictated by the type of colic. Simple spasmodic colics =pond well whereas some obstmctions and displacements of the bowel will only respond with surgical intervention. Surgery is not m option in most developing countties due to economics plus lack of facilities and trained colic surgery t a m s .

The first step in treatment is pain relief. Dipyrone (1 1 mgkg IV or IM) or

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[Am N ~ M - I - E R VOL, 3 - 9(97 P.WE 4

COMMENTS ON

D R E P ~ ~ I E ~ C S HORSES FOR

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Banarnine {flunixin rneglumine 1 mgkg 1V) injections will help stop spasms and ~ l i e v e pain. Specific pain medications like ButorphanoI. (50 to I00 mg per 500 kg) is very beneficial. Elompun (Xylazine 0.25 to .05 m&) may be needed if pain is severe. Avoid prornazine tranquilizers if the animaI is in shock.

A nasogastric tub if available should be passed to check for and relieve ges- b3c tympany (gas) and fluid distention. M i k of Magnesia (to 1 Iitcr for 500 kg) drenched oral ty or p e n via a stornach tube is often beneficial in producing gastric motiliv, For impactions and sand, Thine~al oil (4 Iiters per 500 kg b.w.1 via nasogastric tube or DSS (dioctyj sodium sulfosuccinate 7.5 to 30 g p e r 500 kg) mixed with 3 4 liters of water wit1 help evacuate in some cases. Metamucil (psyllium, 1 cup twice daily in grain) will help evacuate sand. Some horses with severe impactians or shock may need intravenous fluids (10 to 30 liters of saline or lactated ringers IV).

Walking may help in some situations but he handler must be carefuI to avoid injury if the equine is thrashing about. If the heart rate is ov,er 11 0 beats per minute and the membranes are blue the animal is close to death and should be euthanimd (humanety killed).

B e w e most cslics are due ta poor management, prevention is the most cost effective step an owner can take. Since parasites cause up to 90% of colics, zt gaod pamite program is paramount. Horses should be d e w m e d every two tu thre months (refer to the next section on parasite controI), Avoid sudden feed changes, feed only good quality feeds and on a regular schedule, Avoid pout quality roughage that is poor in nutrient value and any spoiled or moldy feeds, Do not give cold water to horses while they are hot f r ~ m work. Do not f e d on the ground, especially on sandy sail. Avoid large quantities af rich Feed like wheat. Be sure the teeth are examined on a regular basis and any paints or irregularities are filed with a denial rasp lo assist in groper chewing.

F ~ v m rhe hawk, Raisitrg Heulth-v Horsa, by Dr: Bob Beede (to be published bv Ch?.irtiw~ Ya~r i t~up MhsimJ andperscmd experience of Ihe ~lrthr.

11 is with much reluctance that we mention drenching (use of liquid medica- tion by mouth) as a method for treating horses with colic. However there are times when no one is availabIe who can pass a stomach tube and the animal might die. IT SHOULD BE DONE AS A LAST RESQRT ONLY WITH AN UNDERSTANDING THAT THERE ARE MAJOR RISKS.

There is no absolutely safe pmcdum. Any time it is done there is a chance that the medication may get into the l u n g via the trachea (windpipe) and lead to death err pneumonia - The animal has to be well restrained. One of the biggest cortrributing factors i s holding the head too high. Use only water soluble medications such as Milk of Magnesia (Human liquid laxative - Magnesium sulfate- Epsom salts ) * - one liter per SQO kg bw or Mag- nesium sulfate 500- 1OOO Gm dissolved jn 1-2 liters o f water per 500 kg body weight. To rehce the risk of problems use only small amounts of medication at a time.

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ECTOPARASITE CONTROL

Migrarion in Body Larvae cast off heir sheaths. Thm h e y pcnelmle the intestinal mu- cosa and arc tamed away by the b l d and lymph, evennrally rc- turning lo the lumen of h e intes- tine where hey grow to adults.

Lsrvac hatch from thc cw and later undergo their fmt mouh

Lar\.ae undcrgo second moult.

Ftnm (he book '"ldent$~'t~iion und Lqk Cvcie-s rfp~rapites Afiicting Donrestic Animals " hy ER. Kavtz at~d R.E Rehrax~ier, THE 01410 STATE UEIIG-ERSITY PRESS; 1 959.

Parasite control is one of the most important aspects of equine health. Internal and external parasites rob the horse of nutri t ion, cause tissue damage and colic, undue stress reduced immunity, and they can introduce disease. it is dificult if not impos- sible to totally eliminate parasites but they must be controlled to an acceptable level for the equine to function at a good healthy level.

External parasites (ectoparasites) live outside the animal and attack the skin and body openings. Internal parasites live in the body of the host animal and are called endoparasites. Due to brevity of this article, we will focus on parasite control mea- sures.

Spraying & Dipping: Many countries supervise the control of ticks and other ecto- parasites with government programs of spraying and dipping. Contact the local gov- ernment agency for help. Dust & Powden: These can be applied topically to help rid the host of parasites. Pour-ons: Organic phosphates can be poured on the back of horses affected with

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ENDOPARASITE CONTROL

EDITOR'S NOTE To READERS

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mites. Two ounces of Dichlorovous per 500 kg horse poured on the back will work as an effective treatment. Wound Care: All wounds should be cleaned and treated with an insecticide to pre- vent blow flies and screw worms. Mixing the insecticide with petroleum jelly will help prevent ectoparasites. Ivermectin: Some blood sucking insects (blood sucking Iice and ticks) we suscep- tible to ivermectin.

No&: insecricaes are potcn~ially d a n g m ~ s drugs A&&&IIa w directions closed'' especially with mixing and dilution, T~earflttents fw tic& and Ike may nsed 10-15 day ircrewuh.

Cleanliness: Keep pens dry and clean, eliminate wet or muddy areas. Pick up and compost manure twice weekly, PaMures: Rutate w i n g areas. Graze young animals sepmtely fmm older h~rses if possible. Do not overgraze. Feed & Water: Avoid manure contarninati~n in water and feeding areas. Feed up off the ground in bunks if possible. Treatment Program: Young animals are more seriously affected by internal para- sites than mature animals. Start mating foals when they are six weeks of ageand treat them every six to eight wecks until two years. Mature horses need dewormifig every NO to three months. Rotate deworming products to avoid resistant parrtsites. Follow directions to ensure proper dosage.

PmducCs: Xvermectin (Eqvalan, Zirrnectrin) is an excclltnt dewoming agent for most para-

sites. This is the only product that effectively kills migrating parasites in the body tissues.

Pyrantel pamaate (Strongid, Imathal) works well except for stomach bots. - Febenda.de (Panacur), mebendazole (TeImin), cambendazole (Camvet), thia- bendazole (Equizole) works well but easily builds resistance and must be rotated and not over used.

Piperazine (Equivet, Wonder Womer) are not very effective in horses. Dichlorovous (Equiguard) and eicholorfon (Anthon, Combot) are oqpnic &us-

phates. Do not use them in pregnant mares. These two products can cause spas modic cdic but it responds well to treatment. The liquid form can be poursd on [he back to rid the horse of mange mites.

From rhe book. ~ i ~ l r ~ H o w by Dr: Boh B e d , to ha ytibllcrhed hy Chrirtlnn W M ~ ~ I M ~ Miwion.

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