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Veterinary Parasitology

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ransmission paths of Neospora caninum in a dairy herd ofrossbred cattle in the northeast of Brazil

anessa Carvalho Sampaio de Magalhãesa, Uillians Volkart de Oliveirab,onia Carmen Lopo Costaa, Ivanildo dos Anjos Santosa,aria Julia Salim Pereirac, Alexandre Dias Munhoza,∗

Departamento de Ciências Agrárias e Ambientais, Universidade Estadual de Santa Cruz (UESC), Campus Soane Nazaré de Andradeodovia Ilhéus Itabuna, Km 16, Salobrinho, Ilhéus 45662-000, BA, BrazilFaculdade de Ciências Sociais e Aplicadas (FACISA), Rodovia BR 101, 1130 Km 808, Santo Antônio Monte, Itamaraju 45836-000, BA,razilDepartamento de Parasitologia Animal, IV, UFRRJ BR-465 Km 7 Seropédica, Rio de Janeiro, RJ, Brazil

a r t i c l e i n f o

rticle history:eceived 5 April 2013eceived in revised form 10 January 2014ccepted 21 January 2014

eywords:eosporosisongitudinal studyertical transmissionorizontal transmission

a b s t r a c t

The aim of this study was to determine the transmission paths of Neospora caninum ina dairy herd of crossbred cattle. Two hundred and ninety animals were grouped accord-ing to the year of their birth to verify the distribution of infection according to age. Theblood of 196 cattle was collected thrice, with an average interval of 210 days, to evaluatethe existence of horizontal transmission in the herd. To evaluate vertical transmission, theblood of 64 calves was collected prior to ingestion of colostrum and from their mothersat parturition. Moreover, 63 family trees were built. The presence of anti-N. caninum anti-bodies was detected using an indirect fluorescent antibody test. The chi-square test (�2)with Yates’ correction or Fisher’s exact test was used to evaluate the relation between theserology and age groups and between the serostatus of cows and their progeny in differentcalvings. A higher seropositivity (p = 0.035) was found in animals born in 2008 comparedto those born in 1997–2007. The serological status of only 13 animals presented changes,of which six (3.1%) became seropositive, indicating a low proportion of horizontal trans-mission. All seropositive cows gave birth to seropositive calves, resulting in 100% verticaltransmission. Sixty-three family trees were constructed. In 29 (46%) of these families, therewere animals seropositive for N. caninum. Congenital infection in relation to the number of
births was estimated from the relation of Mother+ and Daughter+, without significant dif-ferences (p = 0.84) between the number of births and the transmission of the parasite frominfected cows to their progeny. The low proportion of horizontal transmission combinedwith the high proportion of vertical transmission allowed us to conclude that transplacentaltransmission is the principal route of N. caninum infection in the herd.
Please cite this article in press as: Magalhães, V.C.S.d., et al., Trcrossbred cattle in the northeast of Brazil. Vet. Parasitol. (2014)

∗ Corresponding author. Tel.: +55 73 3680 5406/+55 73 3632 3610;ax: +55 73 3680 5406.

E-mail addresses: [email protected], [email protected]. Munhoz).

304-4017/$ – see front matter © 2014 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.vetpar.2014.01.018

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

In the context of cattle breeding, the protozoan Neosporacaninum is an important cause of abortions in cattle world-

ansmission paths of Neospora caninum in a dairy herd of, http://dx.doi.org/10.1016/j.vetpar.2014.01.018

wide (Dijkstra et al., 2002; Kul et al., 2009). To date, dogs(McAllister et al., 1998), coyotes (Gondim et al., 2004), Aus-tralian dingoes (King et al., 2010) and grey wolves (Dubeyet al., 2011) are known as definitive hosts.

dx.doi.org/10.1016/j.vetpar.2014.01.018


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Horizontal transmission in cattle is characterized bythe absence of a relationship between mother and daugh-ter, by the presence of a group of animals positive to N.caninum belonging to the same age group, or by the appear-ance of abortion outbreaks related to the parasite (Dijkstraet al., 2001, 2002, 2003). In herds where vertical transmis-sion is the dominant route, it is possible to observe thatpositive animals are grouped in certain families (Schareset al., 1998) in which the transmission may reach up to95% (Davison et al., 1999), as infected cows present highproportions of transplacental transmission (López-Gatiuset al., 2004a).

The only proven natural form of horizontal infectionto cattle is the ingestion of oocysts released by definitivehosts because transmission by milk has only been verifiedexperimentally (Uggla et al., 1998); moreover, the inges-tion of placenta by cattle does not result in the emergenceof the disease (Davison et al., 2001). In farms with evi-dence of post-natal infection, it is more common to observedogs that eat the placentas and had free access to the feed-ing areas of cattle (Dijkistra et al., 2002), which favors theinstallation of the cattle-dog-cattle cycle, whereas the dogscan expel oocysts even without presenting positive sero-logy against N. caninum (McAllister et al., 1998).

Vertical transmission can be classified as exogenoustransplacental when there is an ingestion of oocysts dur-ing the gestational period or as endogenous due to theresurgence of a latent infection (Trees and Williams, 2005).Despite the efficiency of vertical transmission, horizontaltransmission is necessary to maintain endemic infection ina herd (French et al., 1999).

Longitudinal studies have been carried out to moni-tor the behavior of N. caninum infection in different herds(Moen et al., 1998; Schares et al., 1998; Davison et al., 1999;Dijkstra et al., 2001, 2002, 2003; Pan et al., 2004; Chanlunet al., 2007; Cardoso et al., 2012). However, these studieshave mostly been carried out with purebred animals, pri-marily those of a Dutch breed. Little is known about thebehavior of infection in the crossbred animals (Bos taurustaurus × Bos taurus indicus) used in tropical countries. Thus,this study aimed to determine the transmission paths of N.caninum in a dairy herd consisting of crossbred animals.

2. Materials and methods

2.1. Study location

The study was carried out at Ibicaraí in the Ilhéus-Itabuna Microregion (altitude 47 m; south latitude 14◦70′

and west longitude 39◦03′) in the State of Bahia. This cityis in the Atlantic Forest. Therefore, it houses a large diver-sity of species, including wild canids such as foxes (Vulpesvulpes) and bush dogs (Cerdocyon thous). The annual rain-fall is 1800 mm, with an annual relative humidity of 80%and a mean temperature of 24 ◦C.

2.2. Characteristics of the selected farm


A dairy cattle breeding farm was selected for its his-tory of exposure to N. caninum in cattle and dogs (Galvãoet al., 2011) and its genealogical records of the animals. The

PRESSrasitology xxx (2014) xxx–xxx

selected farm has 135 hectares and a total of 350 cattle. Theherd consists of crossbred animals (1/4 Bos taurus indicus,3/4 Bos t. taurus to 1/4 Bos t. taurus, 3/4 Bos t. indicus) bredin a semi-intensive system. The milk production of 110 lac-tating cows is 1200 L of milk per day with two milkings/dayperformed by a mechanical milking machine with a closedsystem. Feeding is offered in rotational grazing with miner-als provided ad libitum. Adult animals also receive, once perday, a concentrated supplement of corn, soybeans and urea,and calves receive milk and a concentrated supplement ofcorn and soybeans.

Of the 350 animals, 196 were followed to evaluate hor-izontal transmission (Section 2.3), 290 were categorizedaccording to the year of birth (Section 2.4), 64 cows andtheir calves were included in the analysis of vertical trans-mission (Section 2.5), and 260 were grouped for the studyof serological pairing and genealogy (Section 2.6). The sameanimal may have been included in more than one analysis.

Eighteen dogs of both sexes aged between 8 months and11 years were on the farm during the study, with restrictedaccess to the places of cattle transit (including barnyardand pasture). Some of the dogs had access to the placentasreleased by cows when calving. The blood of 18 dogs on thefarm was collected at least once during the study period.

2.3. Horizontal transmission

From February 2009 to May 2010, the blood of 196 ani-mals was collected three times, at intervals of 210 days toevaluate horizontal transmission.

2.4. Categorization of cattle according to the year of birth

At least one sample was collected from 290 animalsolder than six months of age to verify the distribution ofinfection according to age. These 290 animals were dividedinto three categories: animals born from 1998 to 2007;animals born in 2008; and animals born in 2009.

2.5. Vertical transmission

To observe the vertical transmission ratio in the herd,between October 2010 and April 2011, the blood of 64calves and their mothers was collected only once, beforecolostrum ingestion and at the time of parturition, respec-tively. The vertical transmission ratio was calculated takinginto account the mother’s seropositivity at the time ofparturition, although the serological status was previouslydetermined on the basis of three previously performed col-lections. The gamma-glutamyl transferase (GGT) test wasperformed to assess colostrum ingestion (Paré et al., 1995;Davison et al., 1999).

2.6. Mother–daughter serologic pairing and genealogy

Family trees of 260 animals were constructed from therecords of the farm. To minimize the potential influences


of maternal antibodies, calves up to six months of age wereexcluded from the analysis, with the exception of thosein which the serum was obtained before the ingestion ofcolostrum. From the relationship between a seropositive


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other (+) and seropositive daughter (+), a starting pointas established to estimate the congenital infection of off-

pring in relation to the number of calvings, according toijkstra et al. (2003).

.7. Indirect fluorescent antibody test (IFAT) for theetection of anti-N. caninum antibodies

Sera were tested for anti-N. caninum antibodies using anndirect fluorescent antibody test as previously reported byamane et al. (1997) using the strain NC-BA (Gondim et al.,001). Anti-bovine IgG (F4387, Sigma®-Aldrich Inc., USA)nd anti-dog IgG (F4012, Sigma®-Aldrich Inc., USA) weresed as secondary antibodies. The cut-off point was 1:200or cattle (Dubey et al., 1997), with the exception of that foralves with pre-colostrum serum (Section 2.5), which waset at 1:25 (Kyaw et al., 2005), and 1:50 for dogs (Dubeyt al., 1988). The negative and positive controls used in theattle and dogs consisted of animal sera on which serologyas performed in a prior study in the region (Galvão et al.,

011).

.8. Statistical analysis

The chi-square test (�2) with Yates’ correction orisher’s exact test–when the assumptions used to carry outhe chi-square test were not met was used to evaluate theelation between the serology and the age groups, whichere formed on the basis of birth year, and between the

erology of cows and their progeny in different calvings.The seroconversion rate was calculated considering the

umerator as the number of new cases of seroconversionnd the denominator as the time period during which thenimal was exposed to the risk of seroconversion and isxpressed per 100 animals per year at risk.

. Results

.1. Seroconversion

The seroconversion ratio in one of the three collectionsas 6.6% (13/196), and only six animals (3.1%) sero-

onverted to positive (Table 1). Of the 13 animals thatresented changes to their serostatus, were three calvesn = 4), five heifers (n = 37), four cows (n = 150) and one bulln = 5). The seroconversion rate in the studied herd was 5.5er 100 animals/year, with 2.6 cases per 100 animals/yearlassified as positive and 2.19 as negative.

.2. Distribution of animals according to the year of birth

It was observed that of the 290 cattle, 25.64% (10/39)orn in 2009, 36% (19/52) born in 2008, and 19.6% (39/199)orn between 1998 and 2007 were seropositive (Fig. 1),


ith evidence of a statistical relation (p = 0.035) accordingo the chi-square test. The farm’s records revealed that only.7% (9/1298) of all animals were discarded from 1998 upo 2008 due to reproductive problems.

PRESSrasitology xxx (2014) xxx–xxx 3

3.3. Serology of dogs

Of the 18 dogs, nine presented anti-N. caninum antibod-ies in at least one of the visits, with titers varying from 1:50to 1:800. In 2008, at least 10 of the 18 dogs whose bloodhad already been collected were on the farm, and six wereseropositive.

3.4. Vertical transmission

All 64 calves presented GGT values lower than 50 UI/L,confirming the absence of colostrum ingestion. Fifty-onecalves were calved by seronegative mothers and were alsoseronegative. All seropositive cows (11) at calving alsocalved seropositive calves, indicating 100% vertical trans-mission. The serology of the pre-colostral titers of calvesborn with anti-N. caninum antibodies varied from 1:400to 1:6400. Two other cows were seronegative at calvingbut seropositive in the three collections (see study Sec-tion 2.3 “horizontal transmission”). One of the two calved aseropositive calf with titers of 1:800, and the other calveda seronegative calf (Table 2).

3.5. Mother–daughter serologic pairing and genealogy

Seropositive mothers calved seropositive daughters at arate of 71.1% (32/45). The percentage of positive offspringwas 55.5% (5/9) in the first calving, 87.5% (7/8) in the secondcalving, and 71.4% (20/28) after more than two calvings.The difference in the rate of seropositive progeny in viewof the number of calvings was not significant (p = 0.34).

Sixty-three family trees of two to four generations perfamily (average of 2.4 generations) were constructed andanalyzed. In 29 (46%) of these families, the animals wereseropositive for N. caninum. In five of these families, all ani-mals were seropositive, whereas in 16 families, 25% to 90%of the members were seropositive.

In 12 of the family trees, only one animal was positive.In these families, 66.6% of the seropositive animals wereborn in or after 2007: two in 2007, five in 2008, and one in2009.

4. Discussion

During the study period, few cattle became seropositivefor N. caninum, indicating a low horizontal transmis-sion rate. Similar results were observed in other studies(Davison et al., 1999; Hietala and Thurmond, 1999; Lopez-Gatius et al., 2004a; Chanlun et al., 2007; Woodbine et al.,2008; Cardoso et al., 2012), suggesting that the verticaltransmission is the main infection form among cattle. At thefarm, the offer of placentas to dogs is a common practice.However, the dogs had restricted access to the places wherethe cattle were kept, which may have influenced the lowhorizontal transmission rate, contrary to the observationsmade by Dijkstra et al. (2002) in places where dogs had freeaccess to the feeding areas of cattle.


Of the 13 seroconverted cattle in this study, three calvesseroconverted to positive. These calves belonged to thesame age group and the same grouping, all their moth-ers were seronegative, and they were infected after the


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Table 1Seroconversion to Neospora caninum in crossbred cattle from a dairy cattle farm evaluated from February 2009 to May 2010 in Ibicaraí—Bahia.

Category of animal1 First visit2 Second visit Third visit

Age* Serostatus Titers Age* Serostatus Titers Age* Serostatus Titers

Calves 1 Negative – 7 Positive 800 14 Positive 4002 Negative – 9 Negative 16 Positive 2003 Negative – 10 Positive 200 17 Positive 200

Heifers 9 Positive 3200 16 Positive 400 23 Negative –14 Negative – 21 Negative – 29 Positive 40014 Positive 200 21 Positive 200 29 Negative –15 Positive 200 22 Positive 400 29 Negative –21 Negative – 28 Positive 400 35 Negative –

Cows 29 Positive 400 36 Negative – 43 Positive 200** Negative ** Positive 400 ** Positive 40050 Positive 800 57 Negative – 64 Negative –60 Positive 200 67 Positive 800 74 Negative –

Bull 33 Negative – 40 Positive 400 47 Positive 400

1 Based on category in the first collection.
2 Interval of 210 days between each visit.* Months.
** No information.

first collection; these findings indicate a specific infec-tion source, as observed by Dijkistra et al. (2003). Threecows presented changes to their serological status: one topositive and two to negative. The changes to the cows’ sero-logy were related to pregnancy, as they were seropositiveduring pregnancy and seronegative when they were notpregnant. The increased level of antibodies during preg-nancy is a phenomenon observed due to the recrudescenceof a latent infection (Pfeiffer et al., 2002; Andrianarivoet al., 2005). The positive results during the pregnancy


cannot be considered false positive due to the high titers,which reinforces the possibility of fluctuation in the titersof antibodies during the pregnancy, as previously reported

Fig. 1. Distribution of seropositive and seronegative animals for N. caninum in ac

in several studies (Pare et al., 1997; Guy et al., 2001;Andrianarivo et al., 2005; Kyaw et al., 2005; Nogareda et al.,2007; Cardoso et al., 2009).

Three animals that seroconverted to negative at thethird collection were heifers from seropositive mothers.The animals were older than nine months in the first col-lection, which removed the possibility of the maternalantibodies having influenced the results, as maternal anti-bodies are detectable up to the 5th–6th months of age(Hietala and Thurmond, 1999; Cardoso et al., 2008), sug-


gesting that these animals were transplacentally infected.A possible explanation for the conversion to negative at thethird collection is a false-negative test result.

cordance with the year of birth on a dairy cattle farm in Ibicaraí, Bahia.



V.C.S.d. Magalhães et al. / Veterinary Parasitology xxx (2014) xxx–xxx 5

Table 2Pre-colostrum titers of calves and their mothers to Neospora caninum on a dairy cattle farm in Ibicaraí-Bahia.

Cow Serostatus Titers Pregnancy Observations

Parturient Parturient Calf Order

1 Positive 800 6400 1st2 Positive 200 1600 4th3 Negative 0 800 3rd4 Positive 400 400 5th5 Positive 800 800 2nd The 1st pregnancy resulted in abortion6 Positive 800 6400 2nd First parturition after seropositivity7 Positive 800 3200 7th8 Positive 400 3200 3rd First parturition after seropositivity9 Positive 400 1600 4th10 Positive 800 3200 3rd First parturition after seropositivity

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11 Positive 1600 320012 Positive 800 800

13 Negative – –

The seropositivity results of one heifer and one cowlternated between the three collections. It is possiblehat the lack of detection of anti-N. caninum antibodiesn a sample was caused by a fluctuation in titers, caus-ng them to drop below the detection limit, as an animaleropositive at only one timepoint cannot be considered aalse positive due to the titers presented. These animalsere young (average age of 38 months at the last col-

ection), and the variation between collections may haveeen due to a greater instability of titers in young animalshan in adult animals; steadier levels of antibodies may beresent in adults due to prolonged antigenic stimulationfter repeated reactivations of the infection (Jensen et al.,999).

It is likely, as previously mentioned, that some of theesults observed in these 13 animals are due to the pres-nce of titers below the cutoff. In the IFAT, as well as inther diagnostic tests, the cutoff point can be arbitrarilyelected to obtain the sensitivity and specificity requiredor a particular application, but there is no consensus on theold standard (Pare et al., 1995; Dubey, 2003.). Althoughecreasing the cutoff increases the test sensitivity (Scharest al., 1998), studies indicate that a cutoff below 1:160n cattle can increase cross-reactions (Paré et al., 1995).hus, the concomitant use of western blot is recommendedo minimize this occurrence (Álvarez-García et al., 2003;öndgn et al., 2001).

In this study, as complementary diagnostic techniquesere not used, we chose a cutoff of 1:200, which presents

imilar results to a cutoff of 1:100 (Von Blumröder et al.,004) and has been used to compare the IFAT with othererological tests (Reichel and Pfeiffer, 2002; Wapenaart al., 2007). This cutoff minimizes the chance of falseositives (Paré et al., 1995) and ensures good sensitivitynd specificity (Álvarez-García et al., 2003), which wasorroborated by Magalhães et al. (2012), who observedoncordance of 98.5% between collections as well as highensitivity (95%) and specificity (99.4%).

We believe this cutoff would be ideal at 1:200, ensur-ng excellent specificity. Of the 196 animals sampled, 151


ere always negative, and 32 were always positive. Thisutoff was also very effective in characterizing the positivend negative animals that were part of another longitudi-al study that examined the effects of same property on the

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fluctuation of antibodies during pregnancy. In that study,34 cows negative throughout pregnancy kidded negativecalves, whereas of the 12 cows with chronic infection, onlythree showed titers below the cutoff point at some pointduring pregnancy (data not available), and all kidded pos-itive calves.

A greater stability of antibodies in adult animals wasevidenced in this study, as even when horizontal infectionwas characterized in some animals, the number of young(calves and heifers) that seroconverted (8/41) was higherthan the number of adults (5/155), representing a serocon-version rate of 19.51% in young animals and 3.2% in adults.

The distribution of animals in accordance with the yearof birth shows that there was a higher number of pos-itive animals for N. caninum among those born in 2008,most likely due to a common source of infection, suggest-ing horizontal transmission. These findings are similar tothose of Dijkstra et al. (2001), who plotted all seroposi-tive and seronegative animals according to birth month andobserved greater seroprevalence in specific age groups inthe herds of eight farms studied. In this study, the selec-tive discarding of animals practiced in the farm did notinfluence in the lesser number of seropositive animalsborn in 1998–2007, as few animals were discarded due toreproductive problems, reinforcing the higher incidence ofinfection in the group of animals born in 2008 (Fig. 2). How-ever, the number of abortions did not increase with theincreased incidence.

The introduction of dogs onto a farm is considered arisk factor for neosporosis (Dijkstra et al., 2002). In 2008,two dogs were brought to the farm. One of them remainedseronegative in all samples, and the other seroconvertedto positive in 2009. It is probable, then, that the sourceof infection of N. caninum for cattle born in 2008 was notthe dogs introduced that year and was instead dogs thatalready resided on the farm, dogs from other farms, and/orwild canids. We currently, however, do not have evidenceto prove this hypothesis.

Cows with different numbers of calvings transmittedthe infection, and crossbred cows transmit the infection


with N. caninum transplacentally as frequently as pure-bred Dutch cows (Schares et al., 1998; Davison et al., 1999).The high vertical transmission observed by pre-colostrumanalysis was similar to the results found by other authors



6 V.C.S.d. Magalhães et al. / Veterinary Parasitology xxx (2014) xxx–xxx

y cattlees = pos

Fig. 2. Examples of families of cows tested for Neospora caninum on a dairWhite boxes = not tested; gray boxes = negative for N. caninum; black box

(Pare et al., 1997; Wouda et al., 1998; Davison et al.,1999; Waldner et al., 2001), confirming that transplacentaltransmission is the most important route of transmissionamong cattle, either purebred or crossbred, as shown in thisstudy.

All seropositive cows calved positive calves. One ofthe animals that presented higher pre-colostrum titerswas a calf born from the first calving of a cow whosemother was seropositive. These findings confirm the resultsobserved by other authors, in which seropositive primi-parous cows transmitted the infection to their progeny,which were born with high titers of anti-N. caninum anti-bodies (Anderson et al., 1997; Waldner et al., 2001).

The phenomenon observed in one of the cows, whichwas positive in the three collections, gave birth to aseropositive calf, and was seronegative at calving, hasalready been reported by Nogareda et al. (2007). Theseauthors suggested that the negative result may have beendue to a demand of IgG for the colostrum in the last monthof pregnancy or to an excess of antibodies and low numberof antigens, which may interfere in the adequate formationof the antigen-antibody complexes necessary to visualizethe reaction.

Another cow, which was seronegative at calving andseropositive at the three collections, gave birth to aseronegative calf. Some authors have reported that thebirth of seropositive calves is related to high titers duringpregnancy (Pare et al., 1996; Andrianarivo et al., 2005). Inthis study, blood collection during pregnancy allowed fora comparison of the two cows that were seronegative atcalving. The cow that transmitted the infection presenteda peak titer of 1:1600 in the middle third of the preg-nancy, whereas the highest titer observed in the cow thatdid not transmit the infection was 1:800 at the same timepoint, which may partly justify the absence of transmis-sion.

Over 93% (60/64) of the calves that were pre-colostralserology tested were born clinically normal. Of the fourstillbirths, one was serologically positive for N. caninum anddied of anaplasmosis, which was confirmed by physical,laboratory and molecular examination. In the same period,51 cows on the farm were followed during pregnancy (datanot shown), and of these, 13 were N. caninum reactive. Ofthese reactive cows, three aborted and presented a titer of


1:1600 at the time of abortion. Nevertheless, there is needfor further investigation. It is likely that the farm did notpresent a low-virulence strain of N. caninum (Miller et al.,2002; Rojo-Montejo et al., 2009).

farm, demonstrating horizontal infection in 2008/2009 in Ibicaraí, Bahia.itive for N. caninum. Numbers inside the boxes = year of birth.

Finally, because of the possibility of an inefficientimmune response of the fetus (Wouda et al., 1997; Dubeyet al., 1997; Kyaw et al., 2005), the stage of gestation orexposure level (Dubey, 2003), we chose different cutoffpoints, one for calves with pre-colostrum serum (Section2.5) and another for the other cattle farm. However, nocalves with pre-colostrum serum had titers below 1:200(Table 2), which is consistent with the fact that the sero-logical titers of congenitally infected animals are high(Anderson et al., 1997).

Although studies have demonstrated that transplacen-tal transmission decreases with the increase in the numberof pregnancies (Dijkstra et al., 2003; Lopez-Gatius et al.,2004b), this was not observed in our study, as there wasno significant difference between the seropositivity of theprogeny in relation to the number of calvings. This findingmay also be explained in part by the small number of obser-vations analyzed. Similar results were reported by Cardosoet al. (2012), who did not find any relation between age,the number of calvings and congenital infection.

The low horizontal transmission rate and the high ver-tical transmission rate verified in this study indicate thatthe main form of transmission of infection within this herdis vertical transmission, which may also be demonstratedby a larger concentration of infections in specific familiesof cows, as previously observed by Frössling et al. (2005),Schares et al. (1998) and Björkman et al. (1996), as 53.96%of the family trees did not present seropositive animals.

The results of this study show similarity in the transmis-sion of N. caninum in crossbred and purebred animals, witha predominance of transplacental transmission and littleinfluence of horizontal transmission on the positivity of theherd, demonstrating that the adoption of minimum care inthe handling of animals, preventing contact between dogsand cattle, is an important control factor.

Acknowledgements

This work was supported by Fundac ão de Amparo àPesquisa do Estado da Bahia (FAPESB), Conselho Nacionalde Desenvolvimento Científico e Tecnológico (CNPq) andCoordenac ão de Aperfeic oamento de Pessoal de Nível Supe-rior (CAPES-PROCAD/NF-N◦1512/2007).


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transmission paths of neospora caninum in a dairy herd of crossbred cattle in the northeast of...

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