Fractional-order scheme for bovine babesiosis disease and tick populations

This article shows epidemic model, earlier suggested in ordinary differential equation philosophy, can be extended to fractional order on a reliable agenda of biological comportment. A set of domains for the model wherein allvariables are limited is established. Furthermore, the stability and existence of steadiness points are studied. We present the evidence that the endemic equilibrium (EE) point is locally asymptotically stable when reproduction number R0 > 1. This outcome is attained via the linearization statement for fractional differential equations (FDEs). The worldwide asymptotic stability of a disease-free point, when R0 < 1, is also verified by comparison theory for fractional differential equations. The numeric replications for diverse consequences are carried out, and data attained are in good agreement with theoretical outcomes, displaying a vital perception about the use of the set of fractional coupled differential equations to model babesiosis disease and tick populations.


Introduction
Bovine babesiosis (BB) is communicated by the bite of ticks and is the most important disease to attack bovine populations in humid areas. In hot and warm areas there is great financial loss due to bovine death by BB, with decrease of bovine products and by-products. Besides, the environment conditions in those regions favor the survival and reproduction of ticks, so bovines have an enduring interaction with these vectors []. What is more, the vertical spread in bovines and ticks is likely to happen when the ovaries of the female ticks are plague-ridden by parasites []. The behavior dynamics of syndromes has been considered for a stretched period and is an important issue in the real world. The most important model that can be used to interpret the disease characteristic of epidemics is the susceptible-infected-recovered (SIR) model that was developed by Kermack and McKendrick []. Various types of diseases are studied by this type of ordinary differential equation system. Aranda et al. [] introduced the epidemiological model for bovine babesiosis and tick populations disease. In this work the qualitative dynamics behavior is determined by the reproduction number R  . If the threshold parameter R  <  is proved by the LaSalle-Lyapunov theorem, then the solution converges to the disease free equilibrium (DFE) point. However, if R  > , the merging is to the EE point by numerical imitations. In  Leibniz, one of the originators of ordinary calculus, introduced the concept of fractional calculus in a memo transcribed in . In latest eras, FDEs have become one of the most important topics in mathematics and have received much consideration and growing curiosity due to the options of unfolding nonlinear systems and due to their prospective applications in physics, control theory, and engineering [-]. The benefit of FDE systems is that they allow greater degrees of freedom and incorporate the memory effect in the model. Due to this fact, they were introduced in epidemiological modeling systems. In [], a fractional order for the dynamics of A (HN) influenza disease was studied by numerical simulations. Pooseh et al. [] and Diethelm [] introduced fractional dengue models. In this article the parameters of equations obtained in the field research do not reproduce well the evolution of the disease in the case of entire order model. However, when we consider the fractional system with the same parameters obtained in the field, the data are better adjusted, which shows an advantage of the fractional system. In [] the parameter θ is associated with a memory effect. In [], the authors attribute to θ the memory information of the dengue diseases. In this article, we ponder on the fractional order system linked with the development of BB disease and tick populations. We introduce a broad view of the classical model presented by Aranda et al. []. The generalization is attained by changing the ordinary derivative with the fractional Caputo derivative. It is easy to see that when θ =  we return to the classical model. For the construction of this model by Aranda et al. [], the compartments of populations and the biological hypothesis are used. This argument is well established in the disease transmission theory. Aranda et al. use theorems well established in the literature for ordinary differential systems. To prove our results, it is necessary to use tools different from those used for the integer order. This is due to the fact that the versions of La-Salle invariance theorem used by Aranda et al. are not found in the literature for fractional-order systems. Therefore, we emphasize that the work presents collaboration in this direction when using the comparison theory for fractional-order systems to verify the worldwide stability of DFE point of the disease by introducing a new type of results in the literature. On the other hand, we also have a test on the native asymptotic stability of EE point, a result that was just enunciated by Aranda et al. []. We obtain a generalization of all results in []. Our simulation shows that the fractional model has great potential to describe the real problem without the need for adjustment of parameters obtained in the field research. This is due to a greater flexibility of adjustment obtained with the introduction of the new parameter.
Fractional calculus represents a generalization of the ordinary differentiation and integration to non-integer and complex order []. The generalization of differential calculus to non-integer orders of derivatives can be traced back to Leibnitz []. The main reason for using integer order models was the absence of solution methods for fractional differential equations. It is an emerging field in the area of applied mathematics and mathematical physics such as chemistry, biology, economics, image, and signal processing, and it has many applications in many areas of science and engineering [], for example, viscoelasticity, control theory, heat conduction, electricity, chaos and fractals, etc. []. Various applications, like in the reaction kinetics of proteins, the anomalous electron transport in amorphous materials, the dielectrical or mechanical relation of polymers, the modeling of glass forming liquids and others, are successfully performed in numerous papers [].
The physical and geometrical meaning of the non-integer integral containing the real and complex conjugate power-law exponent has been proposed. Finding examples of real systems described by the fractional derivative is an open issue in the area of fractional calculus []. Since integer order differential equations cannot precisely describe the experimental and field measurement data, as an alternative approach, non-integer order differential equation models are now being widely applied [, ]. The advantage of fractional-order differential equation systems over ordinary differential equation systems is that they allow greater degrees of freedom and incorporate memory effect in the model. In other words, they provide an excellent tool for the description of memory and hereditary properties which were not taken into account in the classical integer order model []. The calculus of variations is widely applied for some disciplines like engineering, pure and applied mathematics. Moreover, the researchers have recently proved that the physical systems with dissipation can be clearly modeled more accurately by using fractional representations []. Recently, most of the dynamical systems based on the integer order calculus have been modified into the fractional order domain due to the extra degree of freedom and the flexibility which can be used to precisely fit the experimental data much better than in the case of the integer order modelling.
Purohit and Kalla [] discussed the generalized fractional partial differential equations involving the Caputo time-fractional derivative and the Liouville space-fractional derivatives. The solutions of these equations are obtained using Laplace and Fourier transforms. Also Purohit [] discussed the generalized fractional partial differential involving the Hil- This article is organized in four segments. Introduction is the first segment in which we elaborate on some history of fractional calculus. In Section , we elaborate notations related to the concept of FDEs. In Section , we ponder on the fractional-order model linked with the dynamics of bovine babesiosis and tick populations. Qualitative dynamics of the model are resoluted by the elementary reproduction number. We provide a comprehensive investigation for the global asymptotical stability of DFE point and the native asymptotical stability of EE point. In Section , numerical imitations are offered to validate the main outcomes, and finally conclusion is drawn in Section .

Preliminaries
For several ages, there have been numerous definitions that fit the notion of fractional derivatives [, ]. In this article the Riemann-Liouville fractional derivative, the Caputo fractional derivative, and Grunwald-Letnikov definitions are presented. Firstly, we introduce the definition of Riemann-Liouville fractional integral where ϕ > , f ∈ L  (R + ), and (·) is gamma function.

R E T R
The Riemann-Liouville derivative is given by The Caputo fractional derivative (CFD) is agreed to be as follows: where m is the first integer not less than ϕ.
The Grunwald-Letnikov derivative is given by where [·] means the integer part. The Laplace transform of the CFD is specified by The Mittag-Leffler function is defined by the following infinite power series: The Laplace transform of the functions is Let α, β > , and z ∈ C, and the Mittag-Leffler functions satisfy the equality given by The- for all u, v in the purview of F and ν is the Holder exponent. We represent the space of Holder-continuous functions by G ,ν .
We improve a generalized inequality, in which the core appraisal system is a vector fractional order system.
Consider the fractional order system with the initial condition Let g: F →R m , F ∈R m , we consider the following system of fractional order: Demarcation  We say that E is an equilibrium point of () if and only if g(E) = .
Remark  When ϕ ∈ (, ), the fractional system D ϕ C x(t) = g(x) has identical equilibrium points as the arrangement x (t) = g(x).
The equilibrium points of system () are locally asymptotically stable if all eigenvalues λ i of the Jacobian matrix J, calculated in the equilibrium points, satisfy | arg(λ i )| > ϕ π  .

Mathematical model
In this segment, we introduce the fractional model for the BB in bovine and tick populations. We use the assumptions in Aranda et al.
[] and introduce the following hypotheses.

Fractional order model
In current years, a substantial attention to the fractional calculus has been shown, which allows us to consider integration and differentiation of any order. To a large extent, this is due to the uses of fractional calculus to problems in different areas of research. The benefit of FDE systems is that they allow greater degrees of freedom and incorporate memory effect in the model. Now we describe a new system of FDEs to model the babesiosis disease in bovine and tick populations, and in this system φ ∈ (, ).
Simplifying system (), using the bovine and tick populations' constants T B and T T , respectively, and introducing the proportions we attain the following fractional system that defines the dynamics of bovine quantity in each class: otherwise it is called incommensurate. The chaotic behavior of the system, when the total order of system is less than three, is an interesting topic, and it is connected to the fractal phase space in dynamics. Next we show all variables of the babesiosis model living in for all time t ≥ . To establish our first result, we introduce the following lemma.

Lemma  (see []) Let the function f ∈ C[t  , t  ] and its fractional derivative D
Therefore, considering the interval [, t  ] for any t  > , this theorem infers that the function f : By the same argument, if (U(), V (), Z()) ∈ V -axis, we obtain

R E T R A C T E D A R T I C L E
and if (U(), V (), Z()) ∈ Z-axis, we have This proves that axes U, V , and Z are solutions and positive invariant sets. Now, we will prove that + is a positive invariant set. By way of contradiction, suppose there exists a solution (U, V , Z) such that (U(), V (), Z()) ∈ + and the solution (U, V , Z) to escape of + . From the previous argument and by the unicity of solutions, (U, V , Z) does not cross the axis. After the previous conclusion, there are three possibilities.
(i) If the solution (U, V , Z) escapes by the plane U(t) = , then there exists t  such that U(t  ) = , V (t  ) > , and Z(t  ) > ; and for all t > t  sufficiently near t , we have From Lemma , we obtain U ≥ U(t  ) ≥  for all t sufficiently near t  , and it is not true. (ii) If the solution (U, V , Z) escapes by the plane V (t) = , then there exists t  such that U(t  ) > , V (t  ) = , and Z(t  ) > ; and for all t > t  sufficiently near t , we have ≥  for all t sufficiently near t  , and it is false. Therefore, we obtain U ≥ , V ≥ , and Z ≥  for all t ≥ .
If  ≤ U() + V () ≤ , from the first two equations of system (), we get Applying the Laplace transform in the previous inequality, we have That can be written as From the Laplace transform properties () and (), we infer that Therefore, we have that  ≤ U(t) + V (t) ≤ .

A R T I C L E
On the other hand, if  ≤ Z(t) ≤ , from system () we obtain () The proof of  ≤ Z(t) ≤  is similar to the previous case. Finally, we conclude that is a positive invariant set.

Existence and stability of equilibrium points
There are two equilibrium points of system (). Motivated by Aranda et al.
[], we will use the following threshold parameter. For more details on the threshold parameter, see [, ].
The value that R  yields can specify the situations in which the epidemic is likely. In the drug using context, R  tells us, on average, the total number of people that each single drug user will initiate to drug use through the drug using career.

R 0 sensitivity analysis
To examine the sensitivity of R  to each of its factors,

Stability of DFE
System () has the DFE, i.e., E  = (, , ), for all the values of the factors in this system, whereas only if R  > , there is a (unique) EE point, i.e., E  = (U * , V * , Z * ), where in the interior of .

A R T I C L E
The Jacobian matrix of system () is Now the Jacobian of system () at the DFE (, , ) is Consequently, the eigenvalues of J(E  ) are It is easy to see that λ  and λ  are negative numbers. If R  < , we observe So, Therefore λ  <  and λ  < ; then we have that all the eigenvalues of the Jacobian matrix at E  are negative, i.e., | arg(λ i )| = π , i = , , , and from Theorem , we have that the DFE point E  is locally asymptotically stable. Consequently, we have the following theorem.
Theorem  If R  < , then the disease-free point E  is locally asymptotically stable. Now we will prove the global asymptotic stability of the DFE point.
Theorem  If R  < , then the disease-free point E  is worldwide asymptotically stable.

A R T I C L E
Proof Suppose that (U, V , Z) is the elucidation of system (). Creating the variation of variables M =  -U, we obtain the new system It is easy to see that From the above, it follows that the solutions (M, V , Z) of system () satisfy the differential inequality Moreover, inspired by (), let (S, T, W ) be the solution of the fractional linear system with ICs (S(), T(), W ()) ∈ . The Jacobian of system () is So the Jacobian at the DFE is  Definition  Let Q be any matrix of real and complex numbers with order n × m, let q i  ,...,j k be the minor of A determined by the rows (i  , . . . , i k ) and the columns (j , . . . , j k ), with  ≤ i  < i  < · · · < i k ≤ n, and  ≤ j  < j  < · · · < j k ≤ m. The kth multiplicative compound matrix of Q k of Q is the ( n k ) × ( n k ) matrix whose entries, written in a lexicographic order, are q i  ,...,j k . When Q is an n × m matrix with columns q  , q  , . . . , q k , Q k is the exterior product q  ∧ q  ∧ · · · ∧ q k .

Stability of EE
Definition  Let Q = q ij be an n × n matrix, its kth additive compound matrix of Q k of Q is the ( n k ) × ( n k ) matrix given by Q [k] = |D(I + hQ) (k) | = , where D is a differentiation with respect to h. For any integers i = , . . . , ( n k ), let (i) = (i  , . . . , i k ) be the ith member in the lexicographic ordering of all k-tuples of integers such that  ≤ i  < i  < · · · < i k ≤ i n , then if one entry of i s of (i) does not occur in (j) and j s does not occur in (i), , if (i) differs from (j) in two or more enteries.
Remark  For n = , the matrices Q [k] are as follows: Proof The Jacobian matrix of system () is given in (). From () To see that det(J(E  )) < , we proceed as follows. Since On simplification We can easily see that det(J(E  )) < , because all the parameters are positive constants. Now we will show that det(J [] (E  )) < . For this, Analyzing the terms of equality above, we have Then det(J [] (E  )) < , and from Lemma , the EE point E  is locally asymptotically stable. Hence the end of the proof of Theorem .

Numerical simulations
In this section, we simulate different possible scenarios to check the effect that some values of fractional exponent φ have on the dynamics of bovine babesiosis disease and tick populations. For comparison purposes, we will use the same parameters as Aranda et al. [].

R E T R
with i = , , .

Conclusions
We have obtained the worldwide asymptotical stability of disease-free equilibrium using comparison theory of fractional differential equations since R  < . Therefore the proof that the endemic equilibrium point, when R  > , μ B + α > β B , and μ B + α > β T , is locally asymptotically stable was attained using the linearization theorem for fractional differential equations. Moreover, if R  < , then the system evolves to the endemic equilibrium To return to a disease-free status, the R  value should be greater than . R  <  is achieved when parameters β B and β T are very small or when parameters λ B , μ T , and p are very large. Therefore, a biological strategy to combat babesiosis disease would have to focus on one of these parameters. These results were confirmed by numerical simulations using the Adams-Bashforth-Moulton algorithm. Numerical simulations of an improved epidemic model with arbitrary order have shown that fractional order is related to relaxation time, in other words, the time taken to reach equilibrium. The chaotic behavior of the system when the total order of system is less than three is sketched. A comparison between four different values of the fractional order is shown in Figures , 